Answer:
The thermal decomposition of sodium bicarbonate to produce sodium carbonate carbon dioxide and water. This reaction takes place at a temperature of 250-300°C(140-180°C).
Formula to find the percent composition of an element in a compound is

.
Now enter the variables into the formula.

%
Round to 3 significant figures. 15.897% = 15.9%
The answer is 15.9% H
Density (p) is defined as the mass (m) per unit volume (v) or:
p = m/v
Using this relationship, the volume is:
v = m/p
Using the given values of mass of 80 grams and density of 8 g/cm3, the sample volume is:
v = 80 grams/8 grams/cm3
v = 10 cm3
The final answer is 10 cm3.