Tasks for calculation of percentage concentration of solutions should be performed not only when studying the section of chemistry. Ability to carry out the corresponding calculations can serve good service in everyday life, for example, at recalculation of concentration of solution of acetic acid during conservation of vegetables.
It is required to you
- - calculator.
Instruction
1. Any solution consists of the dissolved substance and solvent. In most cases water acts as solvent. To calculate percentage concentration (or a mass fraction of the dissolved substance) it is necessary to use a formula: W = m (the dissolved substance) / m (solution) x 100%W – a mass fraction of the dissolved substance (or percentage concentration), %iz the same formula it is possible to remove also the mass of the dissolved substance if the mass of solution and percentage concentration of solution are known.
2. Example No. 1. Calculate a mass fraction (as a percentage) of table salt (NaCl) if the mass (NaCl) of 5 g, and the mass of solution (NaCl) of 100 g. In this task it is necessary only to substitute the parameters offered in a condition in a formula: W = m (river in-va) / m (solution) x 100%W (NaCl) = m (NaCl)/m (NaCl solution) x 100%W (NaCl) = 5 g / 100 g x 100% = 5%otvt: W (NaCl) = 5%
3. Example No. 2. Calculate a mass fraction (as a percentage) of bromide of potassium (KBr) if the mass of salt (KBr) of 10 g, and the mass of water of 190 g. Before working with a formula on calculation of percentage concentration, calculate the mass of solution which consists of water and the dissolved substance: m (solution) = m (the dissolved substance) + m (water) Therefore: m (solution of KBR) = to 10 + 190 = 200 gpodstavta in a basic formula the parameters found and specified in a condition: W = m (river in-va) / m (solution) x 100%W (KBr) = m (KBR)/m (solution of KBR) x 100%W (KBr) = 10 g / 200 g x 100% = 5%otvt: W (KBr) = 5%
4. Example No. 3. Calculate percentage concentration of acetic acid (CH3COOH) if the mass of acid (CH3COOH) of 30 g, and the mass of water of 170 g. Calculate the mass of solution which consists of water and acetic acid: m (solution) = m (the dissolved substance) + m (water) Therefore: m (CH3COOH solution) = to 30 + 170 = 200 gpodstavta in a formula necessary parameters: W = m (river in-va) / m (solution) x 100%W (CH3COOH) = m (CH3COOH)/m (CH3COOH solution) x 100%W (CH3COOH) = 30 g / 200 g x 100% = 15%otvt: W (CH3COOH) = 15%