In an experiment to determine the percentage of humus content in a soil, the following results were obtained: mass of dish = 10 gm mass of dish and oven-dry...

To calculate the percentage of humus in the soil sample, we need to use the formula: Percentage of humus = (Loss on ignition / Mass of oven-dry soil) x 100% Where "Loss on ignition" is the weight difference between the dish and oven-dry soil and the dish and soil after heating. Using the given values: Mass of dish = 10 gm Mass of dish and oven-dry soil = 50 gm Mass of dish and soil after heating = 40 gm Mass of oven-dry soil = Mass of dish and oven-dry soil - Mass of dish = 50 gm - 10 gm = 40 gm Loss on ignition = Mass of dish and oven-dry soil - Mass of dish and soil after heating = 50 gm - 40 gm = 10 gm Percentage of humus = (Loss on ignition / Mass of oven-dry soil) x 100% = (10 gm / 40 gm) x 100% = 25% Therefore, the percentage of humus in the soil sample is 25%. The correct option is "25%".