Question

2NH4Cl(s)+Ba(OH)2⋅8H2O(s)→2NH3(aq)+BaCl2(aq)+10H2O(l) The ΔH for this reaction is 54.8 kJ . How much energy would be absorbed if 24.7 g of NH4Cl reacts?

Answer 1

1) Chemical equation

2NH4Cl(s)+Ba(OH)2⋅8H2O(s)→2NH3(aq)+BaCl2(aq)+10H2O(l)

2) Stoichiometric ratios

2 mol NH4Cl(s) : 54.8 KJ

3) Convert 24.7 g of NH4Cl into number of moles, using the molar mass

molar mass of NH4Cl = 14 g/mol + 4*1 g/mol + 35.5 g/mol = 53.5 g/mol

number of moles = mass in grams / molar mass

number of moles = 24.7 g / 53.5 g/mol = 0.462 moles

4) Use proportions:

2 moles NH4Cl / 54.8 kJ = 0.462 moles / x

=> x = 0.462 moles * 54.8 kJ / 2 moles = 12.7 kJ

Answer: 12.7 kJ