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# Help! Chemistry question! I need fast!?

How many grammes of MgO do you get from 10 grammes of Mg and 10 grammes of O2

2Mg+O2--> 2MgO

### 1 Answer

- 1 decade agoFavorite Answer
To do this problem, you need to understand stoicheometry. According to the reaction, for every 2 units (moles) of Mg you start with, you get 2 units (moles) of MgO. For every unit (mole) of O2 you start with, you get 2 units (moles) of MgO. You need to convert the masses you have into moles to see how many units of each material you start with. Then you have to calculate how much ending material you can get from each starting material if the other is in excess. Whichever one will give you less of the ending material is what you are limited by.

An example is if you are making french toast, 2 pieces of bread and 1 egg will give you 2 pieces of french toast. How much french toast can you get if you have 6 pieces of bread and 6 eggs? 6 pieces of bread can get you 6 pieces of french toast and 6 eggs can get you 12 pieces of french toast (if you had enough bread). You are limited by the bread so you can only get 6 pieces of french toast.

But you NEED to convert the grams to moles first because that's the units the reaction equation represents.

Good luck.