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

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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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Mass Percent Formula concept. You can view video lessons to learn Mass Percent Formula. Or if you need more Mass Percent Formula practice, you can also practice Mass Percent Formula practice problems.