The concept of percentage is used in chemistry, biochemistry, physics, the food industry. It is one of ways to express concentration of a component in the total value. If percent – the 100-th share of size, then percentage shows quantity of these shares.
It is required to you
- - handle;
- - note paper;
- - calculator.
Instruction
1. If you need to calculate volume percentage contents substances x, use a formula: % Cv = Vx*100/Vobshch = Vx*100 / (Vx+Vy+ … +Vn), %; where Vx is substance volume; Vobshch is the total amount which consists of volumes - Vx, Vy, … Vn – components of substances.
2. Apply a formula to calculation of mass percentage of substance x: % Cm = Mkh*100/Mobshch = Mx*100 / (Mx+My+ … +Mn), %; where Mx is the mass of substance; Mobshch – the lump which consists of masses – Mx, My, … Mn – components of substances.
3. If necessary to count volume percentage in mass, use a ratio: M = V*p, kg; where M – the mass of substance, kg; V – its volume, m3; p – density, kg/m3.
4. Tasks on finding of percentage of the component which turned out as a result of mixing of two solutions with different concentration meet. For example, it is required to determine the mass percentage of NaCl in the solution which turned out as a result of mixing of 1 l of 10% of solution and 2 l of 20% of solution. Density of solutions of 1.07 g/cm3 and 1.15 g/cm3 respectively.
5. For the decision find the masses of 1 l of 10% of solution and 2 l of 20% - go, using a formula from a step 3. Transfer liters to cm3: 1 l = 1000 cm3. You receive 1.07 kg and 2.30 kg. Put both mass and receive the mass of the mixed solution: 1.07+2.30 = 3.37 kg
6. Having transformed a formula from a step 2, find the mass of NaCl in the first and in the second solution: Msoli1 = 1.07*10/100 = 0.107 kg. Msoli2 = 2.30*20/100 = 0.460 kg. Put this masses and receive the mass of salt in the received solution: 0.107+0.460 = 0.567 kg. On a formula from a step 2 find salt percentage in mix of solutions: 0.567*100/3.370 = 16.83%.