determine the percent by mass of all the elements in the compound magnesium sulfate heptahydrate? how do i start this? mg is 24.31 sulfur is 32.07 and 7 hydrogens for heptahydrate? add them up? 63.436. if i am doing this correctly what do i do next?

First the formula for magnesium sulfate heptahydrate is MgSO4.7H2O (you forgot the O in the part you wrote about 7 hydrogen for heptahydrate as well as the O in SO4).

You are on the right track though.
a. Determine the formula mass for MgSO4.7H2O. That will be 24.31 + 32.07 + 4*16 + 7*18.015. I looked up the molar mass from a calculator on the web and obtained 246.426 but you should confirm that.
b. Now, %Mg = (mass Mg/formula mass)*100
%S = (mass S/formula mass)*100
% O = (mass O/formula mass)*100
etc. [remember you have O in SO4 as well as O in H2O
c. When you finish, all of the percents should add to 100%.
Post your work if you get stuck.

THANKS SO MUCH DRBOB!! I GOT THE CORRECT ANSWER!!!!!

To determine the percent by mass of each element in the compound magnesium sulfate heptahydrate, you need to follow a few steps.

1) Find the molar mass of each element:
- Magnesium (Mg) has a molar mass of 24.31 g/mol.
- Sulfur (S) has a molar mass of 32.07 g/mol.
- Hydrogen (H) has a molar mass of 1.01 g/mol.

2) Calculate the molar mass of the entire compound:
- Multiply the molar mass of each element by its respective subscript (number of atoms present in the formula).

For magnesium sulfate heptahydrate, the formula is MgSO4·7H2O:
- The molar mass of MgSO4 is (24.31 + 32.07 + (4 × 16.00)) g/mol.
- The molar mass of H2O is (2 × 1.01) g/mol.

To calculate the total molar mass of the compound, multiply the molar mass of MgSO4 by its subscript of 1 and the molar mass of H2O by its subscript of 7. Then add the two results together.

3) Calculate the percent by mass of each element:
- Divide the molar mass of each element by the total molar mass of the compound and multiply by 100.

Let's apply these steps to find the percent by mass of each element in magnesium sulfate heptahydrate:

Mg:
24.31 g/mol / total molar mass * 100 = (24.31 g/mol / total molar mass) * 100

S:
32.07 g/mol / total molar mass * 100 = (32.07 g/mol / total molar mass) * 100

H:
(2 × 1.01 g/mol) / total molar mass * 100 = ((2 × 1.01 g/mol) / total molar mass) * 100

Therefore, to calculate the percent by mass of each element in magnesium sulfate heptahydrate, you need the molar mass of the entire compound, which includes both the MgSO4 and H2O components.