객관식
A sample of an unknown gas has a density of 4.75 g/L at 3.00 atm and 45.0 °C. What is the molar mass of the gas?
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2. Atoms & Elements
Calculating Molar Mass
객관식
If you have 644 grams of retinol (C20H30O), how many moles of retinol do you have?
A
3.00 moles
B
0.75 moles
C
2.25 moles
D
1.50 moles
검증된 단계별 안내1
Identify the molecular formula of retinol, which is C20H30O, and use it to calculate its molar mass by summing the atomic masses of all atoms in the formula.
Calculate the molar mass using the atomic masses: Carbon (C) = 12.01 g/mol, Hydrogen (H) = 1.008 g/mol, and Oxygen (O) = 16.00 g/mol. Use the formula: \(\text{Molar mass} = (20 \times 12.01) + (30 \times 1.008) + (1 \times 16.00)\).
Once the molar mass is found, use the given mass of retinol (644 grams) to find the number of moles by applying the formula: \(\text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}\).
Substitute the values into the formula: \(\text{moles} = \frac{644}{\text{molar mass}}\) to calculate the number of moles of retinol.
Interpret the result to determine which of the provided answer choices (3.00, 0.75, 2.25, or 1.50 moles) matches the calculated number of moles.
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