Question

How many grams of \(H_2O\) will be produced from 10g of \(H_2\) in an excess of oxygen?

• A. 90 g
• B. 10 g
• C. 80 g
• D. 100 g

Hint:

Always remember to balance the chemical equation and use molar masses to convert between moles and mass in stoichiometric calculations.

Answer 1

The Correct Option is A

Step 1: Understanding the Reaction
The chemical reaction between hydrogen and oxygen to form water is: \[ 2H_2 + O_2 \rightarrow 2H_2O \] This means that 2 moles of hydrogen gas (\(H_2\)) react with 1 mole of oxygen gas (\(O_2\)) to form 2 moles of water (\(H_2O\)). 
Step 2: Molar Masses and Conversion
Molar mass of \(H_2\) = 2 g/mol
Molar mass of \(H_2O\) = 18 g/mol 
Step 3: Calculate the Amount of Water Produced
Given that 10 g of \(H_2\) are used, we can calculate the moles of \(H_2\) used: \[ \text{Moles of } H_2 = \frac{10}{2} = 5 \text{ mol} \] From the balanced equation, we know that for every 2 moles of \(H_2\), 2 moles of \(H_2O\) are produced. Therefore, 5 moles of \(H_2\) will produce 5 moles of \(H_2O\). Now, we calculate the mass of 5 moles of water: \[ \text{Mass of } H_2O = 5 \text{ mol} \times 18 \text{ g/mol} = 90 \text{ g} \] 
Step 4: Conclusion
The amount of water produced is 90 g. \[ \boxed{90 \text{ g of } H_2O} \]