Answer:
When we talk about a compound's mass percent, we want to know how much of that chemical is in a combination or sample. To calculate the mass percent, we must first know how much of the compound we have and how much of everything else we have.
Assume we have a dish of fruits that weights 100 grammes. We'd want to know how much of the fruit is made up of kiwis. We count the kiwis and discover that there are twenty of them.
To calculate the mass % of kiwis, we must first determine how much they weigh in comparison to the rest of the fruits. Assume the kiwis weigh 40 grammes in total. We may use this data to compute the percentage of kiwis in the fruit:
Mass percent of kiwis = (mass of kiwis ÷ total mass of fruits) × 100%
Mass of kiwis = 40 grams
Total mass of fruits= 100 grams
Mass percent of kiwis= (40 grams ÷ 100 grams) × 100% = 40%
So we can say that the fruits is 40% kiwis.
Similarly, when we want to find the mass percent of a compound in a mixture or sample, we need to know how much of that compound we have and how much of everything else we have. We can use the formula I gave earlier to calculate the mass percent of the compound.
which is Mass percent = (mass of compound consumed ÷ total mass of sample) × 100%
Below here is the answer, but i suggest you should give it a try first :)
Molar mass of the compound = 20 grams/mole
Mass of the compound consumed = 2 moles × 20 grams/mole = 40 grams
Total mass of the sample or mixture = 50 grams
Mass percent of the compound = (40 grams ÷ 50 grams) × 100% = 80%
So the mass percent of the compound in the sample is 80%.