Please give me an example and explain thoroughly
2007-03-13 09:30:49 · 4 answers · asked by svictor24 6 in Science & Mathematics ➔ Chemistry
Total the molar masses(atomic mass) for the substance and divide each part by the whole.
H2O has 2 Hydrogen and 1 Oxygen. Hydrogen weighs 1 unit and Oxygen weighs 16. The total mass of a water molecule becomes 18 units, 16 from oxygen and 2 from the hydrogens.
The percent hydrogen is found by dividing 2/18 and multiplying that value by 100% for an answer of about 11%. Oxygen works out to be the remaining 89%.
The subscripts multiplied by the coefficients tell you how many atoms you have and the table tells you how much each one weighs. Keep track of each component and check that the total is 100%
2007-03-13 09:51:10 · answer #1 · answered by C.W. 2 · 0⤊ 0⤋
First calculate the molecular weight of the compound. Then divide the atomic weight of a specific element by the molecular weight of the compound and multiply by 100. THat is the % of that element in the molecule. If there are two atoms of an element in the formula, multiply the atomic weight of that element by 2 before dividing by the molecular weight. Multiply by 3 if there are tree atoms in the formula and so on. Hope this helps.
2007-03-13 16:52:53 · answer #2 · answered by xox_bass_player_xox 6 · 0⤊ 0⤋
You can calculate the percent of any element in the compound by first finding the formula mass, and then dividing the formula mass by the mass of the element in the formula. That probably made no sense, but here's an example:
H2 O aka water
to find the formula mass you multiply the mass of each element by the number of atoms they have and then add the results.
There are two hydrogen atoms and they each weigh 1.0079(g or amu) you can find the masses of certain elements on the periodic table. oxygen has one atom and weighs 15.999 g
H 2 x 1.0079=2.0158
O 1 x 15.999=15.999
Add these two numbers together to get the formula mass.
2.0158+15.999=18.015 -this is the formula mass
To find the percent of each element, you divide the formula mass by the mass of the element in the compound.
H 2.0158/18.015= .11 -multiply by 100 and get 11%H
O 15.999/18.015= .89 -multiply by 100 and get 89% O
2007-03-13 16:53:26 · answer #3 · answered by buttercup 3 · 0⤊ 0⤋
Let us say we have 10g of water.
Water ..H2O.. Mol.wt. = 2 + 16 = 18 = 1 mole of water.
It can also be expressed in a unit of weight ..g/mol, lb/mol etc.
10g H2O = 10 moles.
Mols. H2 = (10 x 2) ÷ 18g/mol. = 1.111 g/mol = 11.11%
Mols. O = (10 x 16) ÷ 18g/mol. = 8.889 g/mol = 88.89%
2007-03-13 17:16:46 · answer #4 · answered by Norrie 7 · 0⤊ 0⤋