Multiple Choice
How many moles of K_2SO_4 are present in 15.0 g of K_2SO_4? (Molar mass of K_2SO_4 = 174 g/mol)
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2. Atoms & Elements
Mole Concept
Multiple Choice
Which of the following samples contains the greatest number of moles of atoms?
A
18 g of H2O
B
24 g of C
C
32 g of O2
D
58.5 g of NaCl
Verified step by step guidance1
Identify the molar mass of each substance to convert the given mass into moles. Use the periodic table to find atomic masses: H = 1 g/mol, O = 16 g/mol, C = 12 g/mol, Na = 23 g/mol, Cl = 35.5 g/mol.
Calculate the molar mass of each compound: For H\_2O, molar mass = 2(1) + 16 = 18 g/mol; For C (elemental), molar mass = 12 g/mol; For O\_2, molar mass = 2(16) = 32 g/mol; For NaCl, molar mass = 23 + 35.5 = 58.5 g/mol.
Determine the number of moles of each sample by dividing the given mass by the molar mass: moles = mass / molar mass.
Calculate the total number of atoms in each sample. For elemental substances like C and O\_2, multiply moles by the number of atoms per molecule (1 for C, 2 for O\_2). For compounds like H\_2O and NaCl, multiply moles by the total number of atoms per formula unit (3 for H\_2O, 2 for NaCl).
Compare the total number of atoms calculated for each sample to determine which contains the greatest number of moles of atoms.
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