Practice problems

1. Calculate the kilogram atoms of Carbon which weighs 36 kg. (A: 3)
2. Calculate kg of Na of which amount is specified as 3 katom.  (A: 69)
3. Calculate the molecular weight of H2SO4, Na2CO3 and KMnO4 (A: 98, 106, 158)
4. How many kilograms of ethane are there in 210 kmol (A: 6300)
5. Convert 88 kg of carbon dioxide into its kmol (A: 2)
6. Calculate the moles of Oxygen present in 500 g. (A: 15.625)
7. Convert 499 g of CuSO4.5H2O into moles (A: 2)
8. How many moles of H2SO4 will contain 64 kg of S (A: 2)
9. How many moles of K2CrO3 will contain 117 kg of K (A: 1.5)
10. How many kilograms of carbon are present in 64 kg of methane (A: 48)
11. Calculate equivalent moles of Na2SO4 in 644 g of Na2SO4.10H2O crystals (A: 2)
12. Calculate nitrogen content in 100 kg of urea sample containing 96.43% urea (A: 45 kg)
13. How many kg of C2H6 contain 4 katom of carbon (A: 60)
14. How many grams of carbon are present in 264 g of CO2 (A: 72)

Basics

A process refers to any operation or number of operations in series that cause physical or chemical changes in substance or group of substances.

The substance or group of substances under consideration is called a system.

The atomic weight of an element is the mass of an atom on a scale that assigns carbon a mass of exactly 12.

The molecular weight of a compound is the sum of atomic weights of atoms that constitute a molecule of a compound.

Equivalent weight of an element or compound is the ratio of atomic weight or molecular weight to its valence.

Normality is defined as the number of gram-equivalents of solute dissolved in one liter of solution.

Molarity is the number of gram moles

Molality is the gram moles of the solute dissolved in one kilogram of solvent.

Weight percent is the weight of any component expressed as the percentage of total weight of a system.

Volume percent is the pure component volume of any component expressed as a percentage of the total volume of a system.

Mole percent is the moles of any component expressed as the percentage of the total moles of a system.

Mole fraction is the ratio of moles of individual components to the total moles of a system.

Weight fraction is the ratio of weight of individual component to the total weight of the system.

In case of substances existing in gaseous state, the relationship among mass, pressure, temperature and volume must be known.

Ideal gas law (Boyle's law) states that for a given mass of an ideal gas, the product of pressure and volume is constant at constant temperature.

P*V = Constant

or

P*V = n*R*T

P - Absolute pressure in kPa

V - Volume in m^3

T - Temperature in K

n - in kmol

R - Universal Gas Constant = 0.008314 m^3.kPa/(kmol.K)

If P1, V1, T1 and P2, V2, T2 are the pressure, volume and temperature of nmol of a gas at conditions 1 and 2 respectively, (P1*V1)/T1   =   (P2*V2)/T2

At Normal conditions of temperature and pressure (NTP;  Temperature = 273.14 K or 0 C and 

Pressure = 1 atm or 101.325 kPa) the volume occupied by 1 kmol of gas = 22.4136 m^3.

In case of gaseous mixtures, the composition of component gases present in the gas mixture is generally expressed in terms of volume percent. The total pressure exerted by the entire mixture is the sum of pressures exerted by each component of gas molecules.

Partial pressure of a component gas is the pressure that would be exerted by that component gas if it were to be present alone in the same volume and at the same temperature.

Pure component volume of a component gas in a mixture of gases is the volume that would be occupied by that gas if it were present alone at the same pressure and temperature as the mixture.

Dalton's law expresses the additive nature of partial pressure. It states that the total pressure exerted by a gaseous mixture is equal to the sum of partial pressures of component gases.

Amagat's law expresses the additive nature of pure component volumes of gaseous mixtures. It states that the total volume occupied by a gaseous mixture is equal to the sum of pure component volumes.

For gases behaving ideally (that follow the ideal gas law), the partial pressure of a component of a mixture is equal to the product of the total pressure and the mole fraction of that component.

pA = xA * P

Pressure % = Mole% = Volume %

Vapour pressure of a liquid is defined as the absolute pressure at which the liquid and its vapour are in equilibrium at a given temperature. Pure water exerts a vapour pressure of 1 atm or 101.325 kPa at 

373.15 K (100 C).

Raoult's law the equilibrium partial pressure of a component in a gaseous mixture is equal to the product of vapour pressure and mole fraction of the component in liquid phase.

Henry's law states that the partial pressure of a solute gas is proportional to mole fraction of that component in liquid phase. The proportionality can be got rid of by using the "Henry's law constant". This constant is specific to different combinations of solutes and solvents.