Question

Hydrogen cyanide, a highly toxic compound, is made by the following reaction:

2CH₄(g) + 2NH₃(g) + 3O₂(g) → 2HCN(g) + 6H₂O(g)

Given that there is 25.9 g of O₂ are added to 44.8 g of NH₃(with excess CH₄), What is the mass of HCN that can be produced from these reactants?

Answer 1

Molar mass of O2 = 32 g/mol

mass(O2)= 25.9 g

use:

number of mol of O2,

n = mass of O2/molar mass of O2

=(25.9 g)/(32 g/mol)

= 0.8094 mol

Molar mass of NH3,

MM = 1*MM(N) + 3*MM(H)

= 1*14.01 + 3*1.008

= 17.034 g/mol

mass(NH3)= 44.8 g

use:

number of mol of NH3,

n = mass of NH3/molar mass of NH3

=(44.8 g)/(17.03 g/mol)

= 2.63 mol

Balanced chemical equation is:

2CH4(g) + 2NH3(g) + 3O2(g) → 2HCN(g) + 6H2O(g)

3 mol of O2 reacts with 2 mol of NH3

for 0.8094 mol of O2, 0.5396 mol of NH3 is required

But we have 2.63 mol of NH3

so, O2 is limiting reagent

we will use O2 in further calculation

Molar mass of HCN,

MM = 1*MM(H) + 1*MM(C) + 1*MM(N)

= 1*1.008 + 1*12.01 + 1*14.01

= 27.028 g/mol

According to balanced equation

mol of HCN formed = (2/3)* moles of O2

= (2/3)*0.8094

= 0.5396 mol

use:

mass of HCN = number of mol * molar mass

= 0.5396*27.03

= 14.58 g

Answer: 14.6 g