Multiple Choice
At standard temperature and pressure (STP), which of the following substances has a standard enthalpy of formation (ΔH_f^ext{∘}) defined as 0 kJ/mol?
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7. Gases
Standard Temperature and Pressure
Multiple Choice
At standard temperature and pressure (STP), what volume will 35.9 g of hydrogen gas (H_2) occupy?
A
2.0 L
B
18.0 L
C
22.4 L
D
400 L
Verified step by step guidance1
Identify the molar mass of hydrogen gas (H\_2). Since each hydrogen atom has an atomic mass of approximately 1.0 g/mol, the molar mass of H\_2 is calculated as \(2 \times 1.0 = 2.0\) g/mol.
Calculate the number of moles of hydrogen gas using the formula: \(\text{moles} = \frac{\text{mass}}{\text{molar mass}}\). Substitute the given mass (35.9 g) and the molar mass (2.0 g/mol) to find the moles of H\_2.
Recall that at standard temperature and pressure (STP), one mole of any ideal gas occupies 22.4 liters. This is a key concept in gas calculations.
Use the relationship between moles and volume at STP to find the volume occupied by the hydrogen gas: \(\text{volume} = \text{moles} \times 22.4\) L/mol.
Substitute the number of moles calculated in step 2 into the equation from step 4 to find the volume of hydrogen gas at STP.
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