Page 12 - 6273

o
T - temperature, K, T = t + 273;
V - volume of gas, m3, p - gas pressure, Pa, (1 atm = 101325 Pa, 1 mm

Hg = 133,322 Pa);

R = 8,31 J/K • mole - universal gas station.

Based on the formulas of the substances you can give their quantitative

characteristics, in particular, to determine the mass fraction of each chemical

element in the compound.

Mass fraction (ω) shows which part of the mass of the given element is from the

whole mass of substance:

n - the number of atom atoms in the compound;

Ar - atomic mass of the element;

Mr - molecular weight.

Examples of problem solving

Example 1. Determine the mass of three molar calcium hydroxide Ca (OH) 2.

Given: Solution:

ν (Са(OН) 2) = 3 mole Using the formula to determine the amount of

to determine: substance

m (Са(OН) 2) – ?

m
  ;
M

determine the mass of calcium hydroxide: m = ν • M

The molar mass of calcium hydroxide is: M (Ca(OH) 2) = 40 + 2 (16 + 1) = 74

g/mole, then

m = 3 mole·74 g/mole = 222g.

Answer: m (Са(OН) 2) = 222 g.

12