Solutions I

Introduction: What is Solution?
A solution is defined as a homogenous mixture of two or more substances, the composition of which may vary within limits.

The component which is present in larger proportions is termed as a Solvent.
The component which is present in smaller proportions is said to be a solute.

Example – In salt solution, salt is the solute, while water is the solvent.
A solution may exist in gaseous state, liquid state or in solid state.
Alloy is an example of a solid solution.

Types of Solutions:
The common solutions that we come across are those where the solute is a solid and the solvent is a liquid. In fact, substances in any three states of matter (solid, liquid, gas) can act as solute or solvent. Thus there are seven types of solutions whose examples are as follows in the table.

S.No         Solute           Solvent         Example
1.               Gas               Gas             Air
2.               Gas               Liquid          Oxygen in water, Carbonated drinks
3.               Gas               Solids          Adsorption of hydrogen by Palladium
4.               Liquid            Liquid          Alcohol in water
5.               Liquid            Solid            Mercury in Silver
6.              Solid              Liquid           Sugar, salt
7.               Solid             Solid            Metal alloys, Carbon in Iron

Liquid Solutions-

Liquid solutions are those, which have liquids in liquids or solids in liquids, making the final solution, a liquid solution.

Example for a liquid solution is mixing of alcohol in water. Solute alcohol mixes with water, the solvent, to form a liquid solution.

Similarly, a soild, sugar, dissolves to form sugar solution, a liquid solution.
Most of the solutions are liquid solutions and the word solution mostly applies to a liquid solution.

There are three types of solutions : True solution, suspension and a colloid.

Chemistry Solutions-

Solutions are a mixture of solvent and solute. Concentration of a solution is defined as:
“The amount of solute present in a given amount of solution”

Concentration is generally expressed as the quantity of solute in a unit volume of solution.

Concentration = quantity of solute present / Volume of solution

A solution containing a relatively low concentration of solute is said to be a dilute solution and the one with high concentration of solute is said to be a concentrated solution.

Unsaturated Solution-

Solutions are said to be saturated or unsaturated, depending upon the amount of solute present in it.

A saturated solution is one, in which the dissolved and the undissolved solute are in equilibrium with each other.

Thus, a saturated solution cannot dissolve any more solute. The solvent cannot take up any more solute inside.

An unsaturated solution is one, in which the solvent is not saturated with solute and it can take up more solute.

Thus, unsaturated solution can dissolve more solute in it.

Separating Mixtures III

Separating Mixtures III
The elements or substance in mixture can be separated easily by many separating methods to get a pure substance. The substance which contains only one substance and cannot be separated further unless a chemical reaction takes place and that substance is called as pure substance. In order to get pure substances, some process of purification methods and technique are followed.

The technique which is used to improve the quality of the material is called as separation technique. There are many methods and technique of process of purification such as isolation, extraction and purification which is done by according to the nature of the substance.

The techniques of process of purification of substance can be broadly classified in to two types.

Physical separation techniques
Chemical separation techniques

Physical separation techniques – The separation techniques are according to the physical properties such as physical state, boiling point, melting point, solubility, density, specific gravity, electrical and magnetic properties of the substance. Some of the important physical separation techniques are as follows.

Washing – Water is used to remove the impurities from insoluble solids like noble metals and compounds like silica. Sometimes organic solvents are used, where there is a mixture with insoluble compound and soluble impurities to remove impurities.

Decanting – This type of separation can be used when the densities of two liquids that are immiscible in one another. It is also used to separate the light liquid from denser solid.
Filtration – This type is used to separate the liquid from insoluble solid, mostly suspensions.

Chromatography – This type of separation can be used where the separation of substances according to their solubility in water.

Distillation – This type can be used to separate two miscible liquids according to their boiling point, because each liquid has its own boiling point.

Fractional distillation – This type of separation can be used where the mixtures of liquid has minimum difference in their boiling point. Here the distillation is carried out in a detailed manner and such type of distillation is called as fractional distillation which is done in a fractionating column.

Solubility – This type can be used where the compounds in mixture has different in their solubility at a particular temperature, because the different type of compounds has different amount of solubility at a particular temperature.

Electrical and Magnetic separation – This type of separation can be used to separate electrolytes and non-electrolytes, magnetic and non-magnetic substances by using electric and magmatic field respectively.

Chemical separation techniques – This type of separation techniques are used according to their chemical properties of the substance. This type most commonly used to separate salts from its mixture by converting one of the salt as insoluble salt. For example the mixture of solutions of calcium chloride and sodium chloride can be separated by adding of calcium carbonate. In this process the calcium is precipitated as insoluble calcium carbonate then both the substances like sodium and chlorine are separated easily.

The most of the Mixture Separation Methods are used to separate the compounds according to the adsorption and desorption properties of the compounds of a mixture. For example, the activated carbon absorbs or removes colour and odour from the organic compound and magnet can be used to separate iron from sand.

Membrane Separation Process is used when the solution of mixture is in colloidal form. In this process the separation occurs through the semi permeable membrane, which allows only the solvent particles and not solute particles. For example sweat formation through skin and kidney functions.

Simple Harmonic Motion Frequency

” A body is said to be in simple harmonic motion, if it moves to and fro along a straight line, about its mean position such that, at any point its acceleration is directly proportional  to its displacement in magnitude but opposite in direction and is directed always towards the mean position”.

Introduction to Simple Harmonic Motion Frequency

If ‘a’ is the acceleration of the body at any given displacement ‘y’ from the mean position, then for the body to be in SHM.

a  `prop`  – y                  or              a    =    – k y

Where ‘k’ is constant of proportionality. (-) indicates that ‘a’  and ‘y’ are always in opposite directions.

Simple Harmonic Motion Frequency : Explanation

Let us consider a particle ‘P’ moving on the circumference of a circle of radius ‘A’ with uniform angular velocity ‘`omega` ‘. Let ‘O’ be the centre of the circle and XX’ and YY’ are two mutually perpendicular diameters of the circle, s shown in the figure. Let PN be drawn perpendicular to the diameter YY’ from P. 

Simple Harmonic Motion Frequency : Relationship between Frequency and Time Period

The time taken to move once, to and fro about the mean position by the particle is defined as the ‘Time period of SHM. It is equal to the period of oscillation of N along the diameter of he reference circle. But the period of oscillation of N is equal to the period of revolution of P on the reference circle above. Since the angle described in one complete revolution is 2`pi`, the time period of SHM is given by

T = `(2pi)/(omega)`   ,  where ‘`omega`’ is the angular velocity on the reference circle, and is a constant.

The number of oscillations made per second in SHM is known as the frequency of SHM.

Therefore it is given by the reciprocal of the time period.   i.e.,    v  =  `(1)/(T)`

From equation’s (1) and (2), we can write   `omega` = `(2pi)/(T)`  = 2`pi`v.

Hence ‘`omega`’ is also known as the angular frequency. The SI unit of frequency is “hertz”. If one complete oscillation takes place in one second, the frequency of oscillation is equal to 1 hertz (1 Hz)

Simple Motion Experiments

Simple motion experiments

Simple motion experiments 1: Distance/ vs. time graph and Speed vs. time Graphs

This experiment uses light gates to measure the distance and speed of a glider. The glider slides down a sloping air track. Graphs of distance versus time and speed versus time are drawn and students should be able to discover the connections between the two slopes and area under the graph.

Simple motion experiments 2: A racing car

Students are provided with curves of an imaginary racing car. The curves in the experiment shows how the  speed increases under acceleration, how the speed  decreases under braking and how fast it can go around corners which are part of a circle  of differing radius.

Simple motion experiments 3: Stopping Time and stopping Distance

In this experiment students discover the relationships between the time to stop and the distance to stop when a constant braking force is applied to the car. The findings of this experiment are related to road safety.

Simple motion experiments 4: Safe Driving Distance

Here, student study a line of moving cars. Suppose a child walks out onto the road. The reaction time of the drivers involved in the experiment and the stopping ability of the cars depending on its mass, its velocity and force is used to plot the positions of the cars each second as they come to a stop. Students should discover how much distance there should be between cars if they are all to stop safely in an emergency condition.

Simple motion experiments 5: Acceleration

Students study that the increase in speed of a car from rest to v  m/s. Firstly the car is given constant acceleration, then increasing acceleration and finally  decreasing acceleration.  Speed -time graphs are plotted . The slope of the graphs relates to the type of accelerations of the car.

Simple motion experiments 6:Constant Acceleration

The equations of motion for uniform acceleration are derived .They are then  checked using the same way as the Distance vs. time and Speed vs. time Graphs experiment.

Periodic Table III

After the various attempts, scientists were successfully given the arrangement of elements in the form of periodic table. The elements are arranged in this table in such a way that all the similar elements are classified together and dissimilar elements are separated. So the table can be defined as the table in which the similar elements are categorized in vertical column according to their properties.

The First Periodic Table was based on the atomic weight of the elements. The credit for Development of the Periodic Table goes to Mendeleev. He proposed that the properties of elements are the function of the atomic weight. So he divided the table into the two mains Parts of the Periodic Table that are periods and group of table.

The Mendeleev table consists nine vertical columns that are called groups. These groups are subdivided into sub groups. Total nine columns are numbering from zero to VIII. The group zero is for inert gases. Similar seven horizontal rows are periods.

So the main use of his table is that his table classifies all the elements of similar properties and separated the dissimilar elements. There is also a left space for new discovered elements that are placed at the left side of his table and the atomic weight of elements is the basic of his table. But due to some limitations of his table, new modified table was given.

Some of the main defects of his table are the uncertainty of hydrogen atom, similar some elements of high atomic weight are placed before the elements of low atomic weight which was opposite to the law, the uncertain position of lanthanides, actinides, noble gases and isotopes.

So the modern table is based on the atomic number of elements and all the element’s properties are periodic function of their atomic number. So the elements are arranged according to their increasing atomic number so the similar elements are placed together. This is also known as long form of the table. The main Periodic Table Symbols are its groups and periods in which elements are arranged with their symbol and atomic number.

But it depends on the type of table because in some table, elements are arranged with their symbol, atomic number, and valance shell electronic configuration. The repetitions of properties are due to the repetitions of same valance shell electronic configuration after a regular interval.

Thus in long form of table, total seven horizontal periods is present and there is close connection between the electronic configurations of elements while total 18 vertical columns that are called group. All the elements of a group are similar in valance shell electronic configuration.
These are some basic Periodic Table Properties which are used to measure some properties of elements like the ionization enthalpy, metallic nature, oxidation number, atomic radius, ionic radius etc.

Osmosis I

Dilute solutions of non volatile solute possess certain set of properties which do not depend on the identity of solute and their values depend on the molar concentration of solute of the solution. These are colligative properties which include vapour pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure.

Here we discuss osmosis. This shows the flow of solvent in a solution from lower to higher concentration. So when two solutions are separated by the semi permeable membrane, the solvent is passed from the solution of lower concentration to higher concentration of solution. This process of flowing is called osmosis. The semi permeable membrane allows to passage of solvent molecules only but it is restricted for solute particles.

The main reason for the movement is the vapour pressure difference of the solutions. As in this process, the solvent is passed between the pure solvent and a solution, so they do not have same vapour pressure.  The vapour pressure of pure solvent is higher than the solution. Thus the solvent moves spontaneously from the region of higher vapour pressure to lower vapour pressure. So there is net transfer of solvent.

Diffusion and Osmosis are different concept but similar because both involve the movement of solvent.  The diffusion is intermixing of two solutions of different concentrations to form a homogeneous mixture.

And this spontaneous process completes with out semi permeable membrane.  It involves the passage of solute and solvent both. It is not bounded to move the solvent particles only, while the osmosis involves the movement of solvent particles only through semi permeable membrane.

It is also bounded for solutions only but the diffusion can take place in all three states of matter; gas, liquid, and solid. The shrivelling of raw mangoes in salt to pickle, swelling in tissues consuming more salt, adsorption of water by plants through their roots and soil, and meat preservation etc are some Examples of Osmosis in our daily life, while perfumes and air freshener works according to the diffusion process.

Now we discuss Osmotic Potential. This is the excess hydrostatic pressure that produces when the solution is separated from the solvent by a semi permeable membrane. This can also be defined as the extra pressure which should be applied to the solution to stop the movement of solvent particles into solution through a semi permeable membrane.

This is quite different from Tonicity which is a measurement process of this extra pressure or osmotic pressure. It can be classified as hyper, hypo, and isotonic. The solution is isotonic to each other when both have same concentration and there is no any movement.

Hypertonic shows the highly concentrated solution while the hypotonic shows the lower concentration of solution. Thus the osmotic potential can also be defined as the potential of solvent molecules to pass from the hypertonic solution to hypotonic solution through a semi permeable membrane.

Nucleon II

Nucleon II(phy)

To define nucleons, it is a another term for nucleus which is present at the centre of an atom. Nucleons are made of two components such as positively charged protons and neutral charged neutrons. The negatively charged electrons are occupied outside of the nucleus. The atoms are electrically neutral because the number of protons present in the nucleus is exactly equal to the  number of electrons present in the outside of the nucleus and that number is known as atomic number (Z) of the given atom.

One or more number of nuclear particles is joined to gather to make atomic nucleus. Every atom consists of cluster of nuclear particle surrounded by electrons in circular orbits. Hence the nuclear particles are particles present at the center of an atom and that makes the nucleus of an atom.

The mass number of an atom is equal to the number of nucleons present in the atomic nucleus. Hence the mass of nucleon is equal to the sum of the particles such as protons and neutrons present in the atom. The protons and neutrons are held up together inside the nucleus due to the nuclear force. Nucleon Mass is equal to the atomic mass number of an atom, hence it is also called as atomic mass.

Nucleons are two types one is proton and other one is neutron. Both are having approximately same mass about proton is 1.6726X10^-27 kg and neutron is 1.6479×10^-27 kg.

The Proton mass is 0.1 percent lesser than neutron mass, so we cannot make any difference between proton and neutron.

Nucleon number is also called as mass number and is equal to the number of protons plus number of neutrons present in the nucleus of an atom, in other words it is the number of nuclear particle present in the atomic nucleus.

Mass number (A) = Z + N

Where,

Z – Atomic number or number of protons present

N – Number of electrons present

Nuclear binding energy is the energy which is required to break or spilt the nucleus into its individual nuclear particle. It can also expressed as that the energy released when the separate nuclear particle are combined or joined to gather to make nucleus and is associated with strong interaction. The mass of the nucleus of an atom is less than the total of the mass of the individual nuclear particle that forms that nucleus of an atom. The binding energy of the nucleus is equal to the mass difference (ΔM) between the mass of the nucleus and the mass of the summation of the individual nuclear particle. The below mentioned given Einstein’s equations gives the relationship between the

binding energy and the mass difference.

E _{Binding energy} = ΔM c²

Where,

ΔM – Mass difference between the mass of the nucleus and the mass of the                summation of the individual nucleons.(Mass defect)

ΔM = Z x M_p + (A-Z) X M_n – M_nucleus

Where,

Z – Atomic number or number of protons present

M_p – Mass of proton

A – Mass number or Nucleon number

M_n – Mass of neutron

M_Nucleus – Mass of nucleus formed

If we know the binding energy in a nucleus then we can calculate binding energy per nucleon and number of nuclear particle. This binding energy per nucleon is the average energy required to remove each nucleon present in the nucleus. So the stability of the nucleus depends upon the binding energy per nucleon. The stability of the nucleus is directly proportional to the binding energy per nucleon. The binding energy per nucleon formula is as follows,

Binding Energy per Nucleon  = total binding energy  =          Mc2

————————–     —————————

Number of nucleons      Number of nucleons

Nuclear fusion II

Nuclear fusion II (phy)

Before we discussing about nuclear fusion, first we should know the definition of nuclear fusion. To define nuclear fusion, it is a nuclear reaction in which the two atomic nuclei are collide at very high speed and combined to form a single new heavy or large atomic nucleus, which contains larger number of protons or neutrons. Simply, it a process in which the smaller nuclei are fused together to form a massive single nuclei.

It produces large amount of energy because the mass of combination of nuclei will be lower than the sum of the mass of the individual nuclei. Sometime more than two atomic nuclei are combined to form a large atomic nucleolus. Fusion reaction requires larger amount of energy to initiate the reaction, since the positively charged protons which is present in nuclei can repeal with each other when brought close enough together to start fusion. For example the sun generates energy by nuclear-fusion that happens in its core due to the collusion of hydrogen nuclei and the formation of helium nucleus. Fusion is the process that powers active stars and sun.

The reaction that takes place in sun is as follows.

¹₁H + ²₁H ————> ³₂He

³₂ He + ³₂He ————-> ⁴₂ He + 2¹₁H

¹₁H + ¹₁H —————-> ²₁H + ⁰₊₁β

If the combined nuclei mass is less than that of iron generally release energy, while the fusion of nuclei which is heavier than iron will absorbs energy.

Hence, the nuclear-fusion usually occurs only for lighter elements not for heaver elements. For heavier elements, which elements mass is heavier than iron, nuclear fission will yield energy. Nuclear fission is process of splitting of heavy nuclei in to two or more smaller nuclei or bombardment of neutron.

Let we discuss the comparison of Nuclear Fusion vs Fission, both are two different type of energy producing reactions. Both the process are releasing large amount of energy, both involve radioactivity,  and both reactions are occur in nuclear bomb and other nuclear weapons. Fusion requires more energy to start the reaction than the fission but it produces five times enormous amounts of energy per gram of fuel then the fission.

let we discuss the distinguishing between Nuclear Fission vs Fusion, in nuclear fission the higher atomic number of elements are split in to smaller atomic number of elements or nuclei and the fission reactions does not occurs naturally. For example uranium splits in to strontium and krypton by nuclear fission. In nuclear-fusion the two smaller atomic number of nuclei are joint or fuse to form a larger atomic number of elements or nuclei and fusion occurs in stars, such as sun. For example hydrogen and hydrogen fuse to form helium in sun. In fission the starting elements have a higher atomic weight than the fission products, while in fusion the starting elements have a smaller atomic weight than the fusion products.

Nuclear Fusion in Stars is one of the most common examples for nuclear-fusion reaction. The centre of the stars have tremendous amount of pressure and heat energy and the atoms are colloid at very high speed and fuse together to produce even more large amount of energy. Hence, the enormous radiant energy of the stars comes from nuclear-fusion process especially in their centers.

Flocculation

In general all waters such as surface waters contain dissolved and suspended particles which have to remove to make it usable. For the separation of this solid portion of water, two main processes are used; coagulation and flocculation processes.

Let’s first define flocculation. Flocculation definition says that it’s a process of conversion of colloids to suspension by the addition of clarifying agent. The suspension is known as flakes or floc.  Although both process are sound similar but refer to two distinct methods;

• The process in which colloidal particles and very fine solid suspensions are destabilized is known as Coagulation.  This destabilization begins agglomerate of particles in appropriate conditions.

• While Flocculation in the process by which destabilized particles conglomerate into larger aggregates for separation in water treatment.

The Flocculation Water Treatment by using coagulating agent is not a new process. It has been practiced from ancient times. In 2000 BC, Egyptians were used almonds smeared around vessels to clarify river water and Romans used alum as a coagulant in municipal water treatment.

The main purpose for water treatment is to remove turbidity from the water which is a cloudy appearance. Turbidity is mainly because of small suspended particles. The recommended level of turbidity is about 0.1 NTU, while the maximum allowable level is 0.5 NTU. The water treatment process removes turbidity as well as many bacteria suspended in the water. Water treatment is generally used for surface water as it flows over ground to streams, then through rivers and picks up a large quantity of particles caused turbidity and colour. However ground water mainly required aeration as it does not have much turbidity and colure.

The waste water treatment is a three step process but in practice last two steps are generally used. Let’s discuss three steps of water treatment.

• Flash mixing: First step is flash mixer where water is mixed with coagulant chemicals to make an even mixer of chemical and water. This process takes a minute or less. On mixing with more than one minute, the mixer blades will convert newly forming floc into small particles.
• Coagulation: Next step is coagulation. During this step, coagulant chemicals neutralize charges of the fine particles which allowing the particles to come closer together and get suspended in water.
• Flocculation: it is final step of thirty to forty-five minutes during which a gentle mixing brings the fine particles into contact with each other and form end product known as floc. It has clumps of bacteria and particulate impurities settle out in the sedimentation basin.

Enthalpy of Combustion III

Thermochemistry is entirely based on the concept of enthalpy. In 1840 Germain Henri Hess purposed a principle, known as Hess’ law states that;

The enthalpy of a given chemical reaction remains constant and does not depend on the way how the reaction goes to completion.

For a given reaction, enthalpy equals to the difference of enthalpies of products and reactants involve in reaction;

ΔH°_r = Σ ΔH°_{f (products)} – Σ ΔH°_{f (reactants)}

Therefore we can determine the enthalpy of any chemical reaction such as neutralization, combusion, transition etc. Let’s take an example of combusion reaction.  A combusion reaction is always associated with burning in oxygen and exothermic in nature. The product of complete combusion varies with various reactants.

The amount of heat released in combusion of one mole of substance at atmospheric pressure is known as heat of combusion or enthalpy of combusion, denoted as ΔH_com and has negative value.

The combusion of organic compounds like hydrocarbons and carbohydrates is much more common and release carbon dioxide and water.

For example combusion of methane and sucrose can be written as below;

CH_4(g) + 2O_2(g) à CO_2(g) + 2H₂O_(g)                          ΔH_com = -882 kJ mol^-1

C₁₂H₂₂O_11(s) + 12O_2(g) à12CO_2(g) + 11H₂O_(g)        ΔH_com = -5644 kJ mol^-1

The heat released in combusion of sucrose is much more comparing to methane due to more number of carbon atoms in sucrose. When the product of combusion is oxide only, the enthalpy of formation and combusion can appear to be the same. Such as the enthalpies of combustion of graphite is also the enthalpy of formation of carbon dioxide. Therefore the Enthalpy of Combusion of Solid Carbon is as follow;

C(graphite, solid) + O₂(g)  à  CO₂(g)        ΔH_com = -393 kJ mol^-1

Similarly Enthalpy of Combustion of Methanol is;

CH₃OH_(l) + ³/₂O_2(g) —> CO_2(g) + 2H₂O_{(l)                 Δ} H = -726 kj/mol

It can be measured experimentally by burning a known amount of material in Bomb calorimeter by determination of temperature change.

It is sealed pack apparatus sealed to prevent escape of the combusion products and pressurised with oxygen to ensure complete combusion. The known amount of sample is ignited by using a fuse wire in the bomb with a known quantity of a substance of known enthalpy of combusion as a standard.  The initial temperature and temperature after combusion is measured and recorded with the final quantity of fuel. The difference in temperature and amount of substance used to calculate enthalpy of combusion.

The experimental determine value of heat of combusion by Bomb calorimeter is generally less than the accepted value due to some loss of heat to atmosphere.