Multiple Choice
What mass of sulfur (S) contains exactly 4.7 × 10^{22} atoms of sulfur?
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2. Atoms & Elements
Mole Concept
Multiple Choice
Which of the following operations yields the number of moles of solute in a solution?
A
Dividing the molarity (in mol/L) by the volume of solution (in liters)
B
Multiplying the volume of solution (in liters) by the molarity (in mol/L)
C
Dividing the mass of solute (in grams) by its molar mass (in g/mol)
D
Multiplying the mass of solute (in grams) by its molar mass (in g/mol)
Verified step by step guidance1
Recall that molarity (M) is defined as the number of moles of solute per liter of solution, expressed as \(M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}\).
To find the number of moles of solute from molarity and volume, rearrange the formula to solve for moles: \(\text{moles of solute} = M \times V\), where \(V\) is the volume in liters.
Understand that dividing molarity by volume, \(\frac{M}{V}\), does not give moles because the units would be \(\frac{\text{mol/L}}{L} = \text{mol}/L^2\), which is not meaningful for moles.
Recognize that the number of moles can also be found by dividing the mass of solute (in grams) by its molar mass (in g/mol), using the formula \(\text{moles} = \frac{\text{mass}}{\text{molar mass}}\).
Note that multiplying the mass of solute by its molar mass would give units of grams squared per mole, which is not a valid way to find moles.
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