E.9

[NHolmes3L]

For question E.9, it asks to write the formula for Magnesium Sulfate Heptahydrate. How am I supposed to figure our what the formula is.

[SVajragiri_1C]

If you look at the periodic table, magnesium is on the second column, which means it has a charge of +2, and sulfate is a common ion with a charge -2 (SO4 2-). The charges of the two ions add up two zero, so the formula of magnesium sulfate is MgSO4. Since it says heptahydrate, you should know that hepta as a prefix means 7, and hydrate is basically water, so the formula is:
MgSO4 7H20 (The water is attached to the magnesium sulfate)

[Aarushi Solanki 4F]

Magnesium sulfate indicates that the element Mg and the ion SO4 are involved. Because the charge of Mg is 2+ and the charge of SO4 is 2-, they balance out and you need one unit of each. MgSO4 is the magnesium sulfate. Heptahydrate means that there are 7 H2O molecules, as the prefix hepta- means 7 and hydrate means water molecule. MgSO4 7H2O is magnesium sulfate heptahydrate.

[Emma Popescu 1L]

My TA said we will go over writing formulas later in the course and for now they will provide the formulas on the test.