Chemical Solutions and Concentrations

Gen Chem 1: Lecture 6

What does the formula mass of a covalent substance represent?

It represents the numbers and types of atoms composing a single molecule of the substance.

What is another term for formula mass of a covalent compound?

Molecular weight.

How do ionic compounds differ in terms of composition compared to covalent compounds?

Ionic compounds use empirical formulas and formula weights, not molecular weights, because they do not exist as discrete molecules.

What does the formula weight of a compound represent?

The sum of the atomic weights for the atoms in a chemical formula.

How do you find percent composition from a compound?

By measuring the mass of each of its constituent elements and dividing by the total mass of the compound.

What are the three steps to determine the empirical formula from percent composition?

1. Derive the number of moles of each element from its mass. 2. Divide each element’s molar amount by the smallest molar amount to yield subscripts. 3. Multiply all coefficients by an integer, if necessary, to ensure that the smallest whole-number ratio of subscripts is obtained.

What is molarity defined as?

The number of moles of solute in exactly 1 liter of solution, expressed as M = mol solute/L solution.

What happens to the amount of solute during the dilution process?

The amount of solute does not change; only the concentration is lessened by the addition of solvent.

What is the formula used to calculate dilution?

M1L1 = M2L2 or C1V1 = C2V2.

How is mass percentage of a solution component defined?

The ratio of the component’s mass to the solution’s mass, expressed as a percentage.