Multiple Choice
Hydrazine (N2H4) reacts with oxygen to produce water and nitrogen gas according to the equation: N2H4 + O2 → N2 + 2 H2O. How many grams of hydrazine (N2H4) are needed to produce 96.0 g of water (H2O)?
3. Chemical Reactions
Stoichiometry
Multiple Choice
An iron bar weighing 56.0 g reacts completely with excess hydrochloric acid according to the equation: Fe + 2HCl → FeCl2 + H2. What mass of H2 is produced?
A
2.0 g
B
2.0 g
C
1.0 g
D
1.0 g
Verified step by step guidance1
Write down the balanced chemical equation: \(\mathrm{Fe} + 2\mathrm{HCl} \rightarrow \mathrm{FeCl}_2 + \mathrm{H}_2\).
Calculate the number of moles of iron (Fe) using its given mass and molar mass: \(\text{moles Fe} = \frac{\text{mass Fe}}{\text{molar mass Fe}} = \frac{56.0\,\mathrm{g}}{55.85\,\mathrm{g/mol}}\).
Use the mole ratio from the balanced equation to find the moles of hydrogen gas (\(\mathrm{H}_2\)) produced. According to the equation, 1 mole of Fe produces 1 mole of \(\mathrm{H}_2\), so \(\text{moles } \mathrm{H}_2 = \text{moles Fe}\).
Calculate the mass of hydrogen gas produced by multiplying the moles of \(\mathrm{H}_2\) by its molar mass: \(\text{mass } \mathrm{H}_2 = \text{moles } \mathrm{H}_2 \times 2.02\,\mathrm{g/mol}\).
The result from step 4 gives the mass of \(\mathrm{H}_2\) produced when 56.0 g of iron reacts completely with excess hydrochloric acid.
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