How would you prepare a 1 L solution of 3 M MgO?

You need to measure 120.9132 grams of MgO and add to 1 liter of distilled water in a beaker.

Explanation:

Capital M stands for molarity, or moles/liter. So 3 M MgO means 3 moles per liter of MgO.

1 L × = 3 moles MgO

This means you need to measure 3 moles MgO to put into 1 Liter of water.

But you don't know how much that is, so you need to convert moles to grams.

First you need to find how many grams are in 1 mole of MgO.

You can search the molar mass of MgO online to get: 40.3044 g

But if you don't have the internet, use the periodic table to add the masses of Mg and O: 24.305 g + 15.999 g = 40.3044 g

Then write the fraction so that the units cancel out, so you get grams by itself on the top of the fraction.

1 L × × = 120.9132 g MgO

You need to measure 120.9132 grams of MgO and add to 1 liter of distilled water.

the product of the pressure and volume is also constant