What is the mass of one mole of magnesium nitrate Mg(NO_3)_2?

2 Answers
anor277
Jan 2, 2016

Got me! I know that 1 mole of magnesium has a mass of 24.3 g.

Explanation:

And I know that 1 mole of nitrogen has a mass of 14.01 g, and that 1 mole of oxygen has a mass of 15.99 g. Do you think that by adding the masses together, appropriately weighted, i.e. 1xxMg + 2xxN + 6xxO, you would arrive at the formula mass of Mg(NO_3)_2?

After you do that, you could see if your summation is [right.](https://en.wikipedia.org/wiki/Magnesium_nitrate) Good luck.

Costas C.
Jan 2, 2016

It is equal to the molecular weight, 147 grams. Use the mole definition.

Explanation:

Mole is defined as:

n=m/(Mr)

where:

m is the mass in grams.
Mr is the molecular weight of the substance.

The molecular weight of a substance is equal to the sum of the molecular weights of the atoms that constitute it. For these atoms:

Mg:24.3
N:14
O:16

So the molecular weight:

Mg(NO_3)_2=MgN_2O_6
Mr=23+2*14+6*16
Mr=147

Therefore:

n=m/(Mr)

m=n*Mr=1*147=147grams

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