Multiple Choice
How many grams of Li3N can be formed from 1.75 moles of Li, assuming an excess of nitrogen? The balanced equation is: 6 Li(s) + N2(g) → 2 Li3N(s).
3. Chemical Reactions
Stoichiometry
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How many grams of hydrogen gas are required if the goal is to form 5.0 x 10⁵ molecules of ammonia? Assume the nitrogen gas is in excess. N₂ (g) + 3 H₂ (g) → 2 NH₃ (g)
A
0.100 grams
B
0.075 grams
C
0.050 grams
D
0.025 grams
Verified step by step guidance1
Start by understanding the balanced chemical equation: \( \text{N}_2 (g) + 3 \text{H}_2 (g) \rightarrow 2 \text{NH}_3 (g) \). This tells us that 1 molecule of nitrogen reacts with 3 molecules of hydrogen to produce 2 molecules of ammonia.
Determine the number of moles of ammonia needed. Use Avogadro's number \( 6.022 \times 10^{23} \) molecules/mol to convert molecules to moles. Calculate the moles of ammonia by dividing the given number of molecules \( 5.0 \times 10^5 \) by Avogadro's number.
Use the stoichiometry of the reaction to find the moles of hydrogen gas required. According to the balanced equation, 2 moles of ammonia are produced from 3 moles of hydrogen. Set up a ratio to find the moles of hydrogen needed for the calculated moles of ammonia.
Calculate the mass of hydrogen gas needed using the molar mass of hydrogen. The molar mass of \( \text{H}_2 \) is approximately 2.02 g/mol. Multiply the moles of hydrogen by the molar mass to find the mass in grams.
Compare the calculated mass of hydrogen gas to the given options (0.100 grams, 0.075 grams, 0.050 grams, 0.025 grams) to identify the correct answer.
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