4 g H2 gas reacts with 8 g O2 gas to form steam. How many moles of gases are there after the completion of reaction in vessel?
Correct answer: C. 2.0
- A. 3
- B. 3.5
- C. 2.0
- D. 0.5
Explanation
Moles of H2= 4/2=2 moles Moles of O2 =8/32=0.25 moles Consider the balanced chemical equation: 2H2 + O2 --------------------- 2H2O Mole ratio is 1:1 for H2 and O2 Therefore O2 is the limiting reactant which means that 4 moles of H2 react with 2 moles of O2 Therefore, after completion of reaction, we have 2 moles of H2O gas. So option C is correct.
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About Fundamental Concepts of Chemistry
Mole calculations connect mass, number of particles and Avogadro's number, while balanced equations provide the mole ratios used in stoichiometry. Questions cover limiting and excess reactants, theoretical yield and percentage yield, including identifying which reactant is consumed first and comparing the actual product with the maximum possible product.
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