2nh3(g) → n2(g) + 3h2(g) the reaction for the decomposition of ammonia (nh3) can be written as shown. if a student starts with 21.7 g of nh3, how many grams of hydrogen (h2) gas will be produced by the reaction? 1.28 g 32.5 g 2.55 g 3.85 g

3.85 g

Explanation:

1) Balanced chemical equation:

2NH₃(g) → N₂(g) + 3H₂(g)

2) Mole ratios:

2 mol NH₃(g) : 1 mol N₂(g) : 3 mol H₂(g)

3) Convert 21.7 g NH₃ to moles

molar mass of NH₃: 14.007 g/mol + 3×1.008 g/mol = 17.031 g/mol

number of moles = mass in grams / molar mass = 21.7 g / 17.031 g/mol = 1.2741 moles

4) Proportionality

2 moles NH₃ / 3 moles 3H₂ = 1.2741 moles NH₃ / x

⇒ x = 1.2741 × 3 / 2 moles H₂ = 1.911 moles H₂

5) Convert 1.911 moles to grams

molar mass H₂ = 2×1.008 g/mol = 2.016 g/mol

mass in grams = number of moles × molar mass = 1.911 moles × 2.016 g/mol = 3.85 g

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