Multiple Choice
Which formula is used to convert grams of a substance to moles?
2. Atoms & Elements
Mole Concept
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If a sample of sodium chloride, NaCl, contains 73.1 kg, what is its number of formula units?
A
6.12 x 1025 formula units
B
8.42 x 1025 formula units
C
1.09 x 1026 formula units
D
7.53 x 1026 formula units
Verified step by step guidance1
First, determine the molar mass of sodium chloride (NaCl). Sodium (Na) has an atomic mass of approximately 22.99 g/mol, and chlorine (Cl) has an atomic mass of approximately 35.45 g/mol. Add these values to find the molar mass of NaCl.
Convert the mass of the NaCl sample from kilograms to grams. Since 1 kg equals 1000 g, multiply 73.1 kg by 1000 to get the mass in grams.
Calculate the number of moles of NaCl in the sample using the formula: \( \text{moles} = \frac{\text{mass in grams}}{\text{molar mass}} \). Use the mass in grams from the previous step and the molar mass calculated in the first step.
Use Avogadro's number to find the number of formula units. Avogadro's number is \( 6.022 \times 10^{23} \) formula units per mole. Multiply the number of moles of NaCl by Avogadro's number to find the total number of formula units.
Review the calculation steps to ensure accuracy and verify that the number of formula units matches one of the provided options.
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