Multiple Choice
A 0.399 g sample of an unknown gas fills a 550. mL flask at standard temperature and pressure (STP). What is the molar mass of the gas?
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2. Atoms & Elements
Calculating Molar Mass
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What is the mass in grams of 5.90 mol of C_8H_{18} (octane)?
A
114 g
B
673 g
C
46.2 g
D
1,024 g
Verified step by step guidance1
Identify the given information: the amount of substance is 5.90 moles of C\_8H\_{18} (octane).
Determine the molar mass of octane by summing the atomic masses of all atoms in the formula C\_8H\_{18}. Use the atomic masses: Carbon (C) = 12.01 g/mol, Hydrogen (H) = 1.008 g/mol.
Calculate the molar mass of octane using the formula: \(\text{Molar mass} = (8 \times 12.01) + (18 \times 1.008)\) g/mol.
Use the relationship between moles, molar mass, and mass: \(\text{Mass} = \text{moles} \times \text{molar mass}\).
Multiply the number of moles (5.90 mol) by the molar mass of octane to find the mass in grams.
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