Some harder problem for practice in STOICHIOMETRY

1. From the following reaction sequence,
CaC₂ + H₂O ® CaO + C₂H₂
C₂H₂ + H₂ ® C₂H₄
nC₂H₄ ® (C₂H₄)_n
Calculate the mass of polyetheylene which can be produced from 10 kg of CaC₂ Ans. 4375g

2. From the following series of reactions,
Cl₂ + 2KOH ® KCl + KClO + H₂O
3KClO ® 2KCl + KClO₃
4KClO₃ ® 3KClO₄ + KCl
Calculate the mass of chlorine needed to produce 100 g of KClO₄. Ans. 204.5 g

3. Crude calcium carbide is made in an electric furnace by the following reaction :
CaO + 3C ® CaC₂ + CO
The product contains 85% of CaC₂ and 15% of unreacted CaO.
(a) How much CaO is to be added to the furnace charge for each 1000 kg of CaC2 (pure) produced?
(b) How much CaO is to be added to the furnace charge for each 1000 kg of crude product ?
Ans. (a) 1041.5 kg ; (b) 893.7 kg

4. From the following reactions, 2CoF₂ + F₂ ® 2CoF₃
(CH₂)_n + 4n CoF₃ ® (CF₂)n + 2nHF + 4n CoF₂
calculate how much F₂ will be consumed to produce 1 kg of (CF₂)_n. Ans. 1.52 kg

5. A mixture containing KClO₃, KHCO₃, K₂CO₃ and KCl was heated, producing CO₂, O₂ and H₂O gases according to the following equations :
2KClO₃(s) ® 2KCl(s) + 3O₂
2KHCO₃(s) ® K₂O(s) + H₂O(g) + 2CO₂(g)
K₂CO₃(s) ® K₂O(s) + CO₂(g)
The KCl does not react under the conditions of the reaction. If 100.0 g of the mixture produces 1.80 g of H₂O, 13.20 g of CO2 and 4.0 g of O₂, what was the composition of the original mixture ? Ans. (KClO₃ : 10.2 g, KHCO₃ : 20g, K₂CO₃ : 13.8 g

6. A natural gas sample contains 84% (by volume) of CH₄, 10% of of C₂H₆ , 3% of C₃H₈ and 3% of N₂. If a series of catalytic reactions could be used for converting all the carbon atoms of the gas into butadiene, C₄H₆, with 100% efficiency, how much butadiene could be prepared from 100 g of the natural gas ? Ans. 82 g

Thermodynamics

Question-1 True or false?

(a) On the Celsius scale, the boiling point of water at standard pressure is 100.00°C.

(b) Doubling the absolute temperature of an ideal gas at fixed volume and amount of gas will double the pressure.

(c) The ratio PV/mT is the same for all gases in the limit of zero pressure.

(d) The ratio PV/nT is the same for all gases in the limit of zero pressure.

(e) All ideal gases have the same density at 25°C and 1 bar.

(f) All ideal gases have the same number of molecules per unit volume at 25°C and 10 bar.

1. Solutions

(a) True: at standard pressure, the Celsius scale uses 100°C as a reference point.

(b) True: the pressure of an ideal gas is directly proportional to its temperature.

(c) False: Avogadro's hypothesis refers to the number of molecules or atoms of a given

volume. Two equal volumes under the same conditions need not have the same mass (m)

even though they have the same number of molecules.

(d) True: see (c) (e) False: see (c) (f) True: see (c)