Problem: A metal (M) forms an oxide with the formula M2 O.If the oxide contains 16.99 % O by mass, what is the identity of the metal?

FREE Expert Solution
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FREE Expert Solution

Step 1: Calculate the mass of M and O in the compound


100% = % mass O + % mass M 

% mass M = 100% - % mass O

% mass M = 100% - 16.99% O

% mass M = 83.01% M


Recall that mass percent is given by:

% mass = mass of Xtotal mass×100

.

Assuming we have 100 g of the compound, this means we have

mass of M = 83.01 g M

mass of O = 16.99 g O.


Step 2: Determine the moles of M and O


We are given the formula of the compound which is M2O. This means the lowest whole number ratio of 2 M: 1 O


Now, we need to get the moles of each element in the compound. 

16.99 g O ×1 mol O16 g O = 1.06 mol O


Since the lowest whole number ratio of M and O is 2: 1, the number of moles of M is twice the number of moles of O. So

number of moles of M = 2×number of moles of O

number of moles of M = 2.12 mol


Step 3: Determine the molar mass of M


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Problem Details

A metal (M) forms an oxide with the formula M2 O.

If the oxide contains 16.99 % O by mass, what is the identity of the metal?

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