Answer to Question #165235 in General Chemistry for Smayya Ruganyira

Question

8. When hydrogen gas was passed over x g of strongly heated copper (II) oxide until there was no further change, 4 g of a solid was formed. (Atomic mass: Cu = 64, O: 16)

a) State what was observed.

b) Write the equation for the reaction.

c) Determine the value of X.

9. Describe the industrial preparation of nitric acid from ammonia (the diagram is not required). Your description should include equations for reactions that occur.

10. The formation of methanol from hydrogen and carbon monoxide is represented by the equation:

2H2(g) + CO(g)———>CHsOH(g) ; the energy released = 92kJ /mol.

Calculate the energy that is released, in kJ/mol, when 96g of methanol is formed. (Relative mass: C= 12, H= 1 and o= 16)  

11. Magnesium reacts with steam to give solid X and gas y.

a) Identify: 

(i) Solid X.

(ii) Gas Y.

b) Describe how Y could be tested.

c) Write the chemical equation for the reaction between X and hydrochloric acid.

Answer 1

8) a. A black mass of Copper (I) oxide

b. 2CuO(s) + H2(g) ---> Cu2O(s) + H2O(g)

c. From the balanced equation,

2mol of CuO gives 1mol of Cu2O

Molar mass of CuO= 80g/mol

Molar mass of Cu2O= 144g/mol

160g of CuO gives 144g of Cu2O

xg of CuO will give 4g of Cu2O

x= 160/144 x 4 = 4.44g of CuO

9) Nitric acid is produced by the industrial method called Oswald process. The starting materials, Ammonia and oxygen are heated in the present of Platinum-Rhodium alloy catalyst to about 1000°C

4NH3(g) + 5O2(g) ---> 4NO(g) + 6H2O(g)

The nitric oxide is subsequently oxidized to nitrogen dioxide

2NO + O2 ---> 2NO2

When dissolved in water, NO2 forms both Nitrous and Nitric acid.

2NO2 + H2O ---> HNO2 + HNO3

10) molar mass of methanol= 32g/mol

32g of methanol generated 92KJ of energy

96g of methanol will generate 92/32 x 96= 276KJ of energy

Therefore, 276KJ of energy will be released when 96g of methanol is formed.

11) I. MgO

II. H2(g)

b. By introducing a lighted splint into a jar containing gas Y. The splint burns with a pop sound.

c. MgO + 2HCl ---> MgCl2 + H2O