An oven dried soil sample of mass 8g had a mass of 1.6g after it was completely burnt. Determine the percentage of humus in the soil sample.

To determine the percentage of humus in the soil sample, we need to first calculate the mass of the humus that was present in the original soil sample. Humus is the organic matter in soil that remains after the decomposition of plant and animal residues. The mass of the humus in the original soil sample can be calculated by subtracting the mass of the burnt soil from the mass of the oven-dried soil: Mass of humus = Mass of oven-dried soil - Mass of burnt soil Mass of humus = 8 g - 1.6 g Mass of humus = 6.4 g Therefore, the mass of humus in the soil sample is 6.4 g. To calculate the percentage of humus in the soil sample, we need to divide the mass of humus by the mass of the original soil sample and then multiply by 100: Percentage of humus = (Mass of humus / Mass of original soil sample) x 100% Percentage of humus = (6.4 g / 8 g) x 100% Percentage of humus = 80% Therefore, the percentage of humus in the soil sample is 80%. So, option D is the correct answer.