Epsom salts is magnesium sulfate heptahydrate. If a student takes 2.50 g of Epsom salts and heats it to drive off the water, how much mass should the student expect to lose? ( I know that hepta is 7 but that's still not making sense to me)

There is a long way and a short way. Here's the long way (the modern way).

MgSO4.7H2O ==> MgSO4 + 7H2O

mols MgSO4.7H2O = grams/molar mass = approx 0.0101
Convert that to mols H2O. That will be 7x that or 0.0707 which you get from the coefficients in the balanced equation.
Now convert to g H2O. mols x molar mass = approx 1.3 g H2O.

The short way which no one teaches anymore. It's (the 7*molar mass H2O/molar mass MgSO4.7H2O) is called a chemical factor but it disappeared from text books years ago.
2.50 g x (7*molar mass H2O/molar mass MgSO4.7H2O) = 2.5 x (18/246.5) = about 1.3g

You can clean up the math since I estimated the numbers.

To determine the amount of mass students should expect to lose when heating Epsom salts to drive off the water, we need to understand the chemical composition and molecular structure of Epsom salts.

Epsom salts, scientifically known as magnesium sulfate heptahydrate (MgSO4 · 7H2O), consists of magnesium sulfate (MgSO4) molecules bonded with seven water (H2O) molecules. The "heptahydrate" indicates that Epsom salts contain seven water molecules per molecule of magnesium sulfate.

The molar mass of magnesium sulfate can be calculated by adding the atomic masses of all the atoms it consists of. Magnesium (Mg) has an atomic mass of around 24.31 g/mol, sulfur (S) has an atomic mass of around 32.06 g/mol, and oxygen (O) has an atomic mass of around 16.00 g/mol. Adding them together, we get:

Mg: 24.31 g/mol
S: 32.06 g/mol
O: (16.00 g/mol) x 4 = 64.00 g/mol

Molar mass of MgSO4 = 24.31 + 32.06 + 64.00 = 120.37 g/mol

Since each molecule of Epsom salts contains 7 water molecules, we need to calculate the molar mass of water as well. The atomic mass of hydrogen (H) is around 1.01 g/mol, and oxygen (O) is around 16.00 g/mol. Adding them together, we have:

H: 1.01 g/mol
O: 16.00 g/mol

Molar mass of H2O = (1.01 g/mol) x 2 + 16.00 g/mol = 18.02 g/mol

Now, we can calculate the molar mass of Epsom salts:

Molar mass of MgSO4 · 7H2O = 120.37 g/mol + (18.02 g/mol x 7) = 246.47 g/mol

With the molar mass calculated, we can now determine the mass of Epsom salts that corresponds to the given 2.50 g. This can be done using the molar mass as a conversion factor:

Mass of Epsom salts (g) = (Number of moles) x (Molar mass)

Number of moles = Mass (g) / Molar mass

Plugging in the values:

Number of moles = 2.50 g / 246.47 g/mol ≈ 0.0101 mol

Now, since the water is driven off when heated, we need to determine the total mass of water in 2.50 g of Epsom salts. Since there are 7 water molecules for every 1 molecule of magnesium sulfate, we can multiply the number of moles by the molar mass of water:

Mass of water lost (g) = Number of moles x Molar mass of H2O

Mass of water lost = 0.0101 mol x 18.02 g/mol ≈ 0.181 g

Therefore, students should expect to lose approximately 0.181 grams of mass when heating 2.50 grams of Epsom salts to drive off the water.