Question #755d3
1 Answer
Percent means "out of 100." So percent composition refers to how many parts (grams, litres, moles, etc.) there are in 100 parts (grams, litres, moles, etc.) of a substance.
Chemists use four types of percent composition.
Percent by mass (m/m)
Mass percent is the mass of a component divided by the total mass of the sample, multiplied by 100%.
Percent mass by volume (m/v)
Volume percent is the mass of a component divided by the volume of the sample, multiplied by 100%.
Example: What is the mass by volume percent of NaOH if you dissolve 5.00 g of NaOH in enough water to make 100 mL of solution?
Percent by volume (v/v):
Volume percent is the volume of a component divided by the volume of the sample, multiplied by 100%
Example: What is the volume percent of ethanol in a 750 mL bottle of wine that contains 94 mL of ethanol?
Mole percent is the moles of a component divided by the total moles of the sample, multiplied by 100%
Example: A solution contains 1.00 mol of NaOH in 5.00 mol water. What is the mole percent of NaOH?
Total moles = 1.00 mol + 5.00 mol = 6.00 mol