A metal oxide has a relative formula mass (Mr ) of 81. The formula of this metal oxide is MO. Given that the relative atomic mass (Ar ) of oxygen is 16, what is the metal in the metal oxide?

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The formula of the metal oxide is MO, which means there is only one oxygen atom bonded to the metal. The Mr of a compound is the sum of Ar of the elements that make up the compound. So, from this we can construct a equation.

Mr of MO = Ar of oxygen + Ar of metal

81 = 16 + Ar of metal

We can then rearrange the equation to give the Ar of the metal.

Ar of metal = 81 - 16

Ar of metal = 65

By looking at a periodic table we can see that the metal that has an Ar of 65 is Zinc. 

Jack T. GCSE Chemistry tutor, A Level Chemistry tutor

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