Multiple Choice
How many grams of alum (KAl(SO4)2·12H2O) can be produced from 20.0 g of aluminum (Al) when the reaction proceeds with 100% yield?
3. Chemical Reactions
Stoichiometry
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
How many grams of sodium metal are needed to generate 4.00 L of hydrogen gas at STP from the reaction with water?
A
4.60 grams
B
9.20 grams
C
18.40 grams
D
2.30 grams
Verified step by step guidance1
Start by writing the balanced chemical equation for the reaction between sodium metal and water: .
Use the ideal gas law to determine the number of moles of hydrogen gas produced. At STP (Standard Temperature and Pressure), 1 mole of gas occupies 22.4 L. Therefore, calculate the moles of hydrogen gas: .
From the balanced equation, note the stoichiometry: 2 moles of Na produce 1 mole of . Use this ratio to find the moles of sodium needed: .
Calculate the mass of sodium required using its molar mass. The molar mass of sodium (Na) is approximately 23.0 g/mol. Use the formula: .
Finally, compare your calculated mass of sodium to the given options to determine which is correct.
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