You will need

- calculator.

Instruction

1

Any solution consists of a solute and solvent. In most cases the solvent is water. To calculate the percentage

**concentration**(or mass fraction of the solute), you must use the formula:W = m (solute) / m (**solution**) x 100% W – mass fraction of solute (or percent concentration), %From the same formula, we can deduce the mass of solute if you know the mass**of the solution**and percent concentration**of a solution**.2

Example No. 1. Calculate the mass fraction (percentage) of salt (NaCl) if the mass of (NaCl) 5 g, and the mass

**of the solution**(NaCl) 100 g. In this problem, it remains only to substitute in the formula proposed in the condition parameters:W = m (b.-VA) / m (R-RA) x 100 % W (NaCl) = m (NaCl) / m (**solution**NaCl) x 100 % W (NaCl) = 5 g / 100 g x 100 % = 5 %Answer: W (NaCl) = 5 %3

Example No. 2. Calculate the mass percent ( % ) potassium bromide (KBr), if the mass of salt (KBr) 10 g, and the weight of water, 190 g Before using formula to calculate percentage concentration, calculate the mass

**of the solution**, which consists of water and dissolved substances:m (**solution**) = m (solute) + m (water) Consequently:m (R-RA KBr) = 10 grams + 190 grams = 200 godstate in the basic formula are found and specified in the condition parameters:W = m (b.-VA) / m (R-RA) x 100 % W (KBr) = m (KBr) / m (**solution**KBr) x 100 % W (KBr) = 10 g / 200 g x 100 % = 5% Answer: W (KBr) = 5 %4

Example No. 3. Calculate the percentage

**concentration**of acetic acid (CH3COOH), if the mass of the acid (CH3COOH) and 30 g, and the mass of water 170 g. Calculate the mass**of the solution**, which consists of water and acetic acid:m (**solution**) = m (solute) + m (water) Consequently:m (R-RA CH3COOH) = 30 g + 170 g = 200 godstate in the formula of required parameters:W = m (b.-VA) / m (R-RA) x 100 %W (CH3COOH) = m (CH3COOH) / m (**solution**CH3COOH) x 100 % W (CH3COOH) = 30 g / 200 g x 100 % = 15% Answer: W (CH3COOH) = 15 %