Question

Determination of physical properties: A 12.0 g sample of wood was collected and dried. After drying, the mass of the sample was exactly 11.50 g. What was the percentage by mass of water in the original sample? If the wood sample had 2.5% ash by mass, what was the mass of the original sample (dry matter) on an ash free basis?

Answer 1

After drying 0.5g is lost. This must be mass of H2O
Hence, taking (0.5/12.0)x100% = 4.1667% by mass of original sample is water.
If wood was ash free,
(2.5/100)x12.0 = 0.3 g is ash
Dried matter was 11.50g
Deducting 11.50- 0.3 = 11.20g which is mass of original dry matter that is ash free.