00:01
In order to find the percentage of an element, the x, in a compound, we will take the ratio of the total molar mass of the element x and the molar mass of the compound.
00:17
Since we're expressing it in percent, we're going to multiply the ratio by 100.
00:24
So consider calcium phosphate, the formula of which is ca3, b042.
00:31
We want to find the following letter a, percentage.
00:35
Of phosphorus in the compound and letter b the mass it's expressing kilograms of calcium phosphate that will deliver 15 kilograms of phosphorus so let us start we're going to find the molar mass of the calcium phosphate the molar mass is found by taking the sum of the atomic mass of all the atoms that make it up so the formula gives three calcium multiplied by the molar mass of calcium which is its atomic mass as expressing grams per mole that is 40 so we get 120 so this we consider as the total molar mass of calcium in the compound next we proceed with phosphorus we have two times 31 which is its molar mass that's 62 for oxygen we count four oxygen in phosphate but since there are two phosphate in in the formula of calcium phosphate therefore that's a total of 8 that's 4 times 2 so we have 8 multiplied by 16 which is the modern mass of oxygen and that gives us 128 therefore the motor mass of the compound is obtained by simply adding them together and this gives us 310 grams per more and so now we find the percentage of phosphorus as the total molar mass of phosphorus, that's 62, divided by the molar mass of the compound, which is 310, multiplied the ratio by 100.
02:22
And this gives us 20%.
02:26
So the percentage of phosphorus in calcium phosphate is 20%.
02:33
This also means that we have 20 kilograms of p per 100 kilograms of calcium phosphate...