Multiple Choice
A solution is prepared by dissolving 98.6 g of NaCl in enough water to form 875 mL of solution. Calculate the mass percent of NaCl in the solution if the density of the solution is 1.06 g/mL.
3. Chemical Reactions
Mass Percent
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What is the mass percentage of carbon (C) in caffeine, C₈H₁₀N₄O₂? Provide an answer to two decimal places.
A
54.12%
B
49.48%
C
58.84%
D
42.09%
Verified step by step guidance1
Determine the molar mass of caffeine (C₈H₁₀N₄O₂) by adding the atomic masses of all the atoms in the formula. Use the periodic table to find the atomic masses: Carbon (C) = 12.01 g/mol, Hydrogen (H) = 1.01 g/mol, Nitrogen (N) = 14.01 g/mol, and Oxygen (O) = 16.00 g/mol.
Calculate the total mass of carbon in one mole of caffeine. Since there are 8 carbon atoms in caffeine, multiply the atomic mass of carbon by 8: 8 × 12.01 g/mol.
Calculate the total molar mass of caffeine by adding the contributions from all the atoms: (8 × 12.01) + (10 × 1.01) + (4 × 14.01) + (2 × 16.00).
Determine the mass percentage of carbon in caffeine by dividing the total mass of carbon by the total molar mass of caffeine and then multiplying by 100 to convert it to a percentage.
Round the mass percentage of carbon to two decimal places to match the required precision.
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