Textbook Question
Calcium hydride reacts with water to form calcium hydroxide and hydrogen gas. (b) How many grams of calcium hydride are needed to form 4.500 g of hydrogen?
3. Chemical Reactions
Stoichiometry
Multiple Choice
The volume of HCl gas required to react with excess Mg metal to produce 6.82 L of hydrogen gas at 2.19 atm and 35°C is ________ L. 2 HCl (g) + Mg (s) → MgCl2 (s) + H2 (g)
A
27.28 L
B
13.64 L
C
6.82 L
D
3.41 L
Verified step by step guidance1
Identify the balanced chemical equation: 2 HCl (g) + Mg (s) → MgCl2 (s) + H2 (g). This tells us that 2 moles of HCl produce 1 mole of H2.
Use the ideal gas law to find the number of moles of hydrogen gas produced. The ideal gas law is given by: , where P is pressure, V is volume, n is moles, R is the ideal gas constant, and T is temperature in Kelvin.
Convert the temperature from Celsius to Kelvin by adding 273.15 to the Celsius temperature: .
Rearrange the ideal gas law to solve for n (moles of H2): . Substitute the known values: P = 2.19 atm, V = 6.82 L, R = 0.0821 L atm/mol K, and T in Kelvin.
Use the stoichiometry from the balanced equation to find the moles of HCl needed. Since 2 moles of HCl produce 1 mole of H2, multiply the moles of H2 by 2 to find the moles of HCl. Then, use the ideal gas law again to find the volume of HCl gas required at the same conditions.
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