A hydrocarbon has a molar mass of 180 g/mol and contains 70% carbon atoms by mass. What is the mass percentage of hydrogen atoms?
Q1. A hydrocarbon has a molar mass of 180 g/mol and contains 70% carbon atoms by mass. What is the mass percentage of hydrogen atoms?
Answer: 18%
Explanation: Atomic mass of C is 12; hence 70/12 = 5.83 moles of C per mole of compound. Mass of 5.83 moles of C is 70g, leaving 110g for H (180-70g). Hence, %H = (110g / 180g) * 100 = 61.11%. Option B is the closest due to rounding.