Verified Answer :

NobleAlexander

I'll be using dimensional analysis to help out.

2.5mol Na2O ( X gNa2O / 1 molNa2O) = ? gNa2O 

X gNa2O is the molar mass of the molecule. To find that we must add up the molar masses of all of the elements in the molecule. 

There are 2 Na (Sodium). 
And 1 O (Oxygen). 

The Molar Mass of Na = 2 22.99 g/mol (It's multiplied by 2 because there are 2 of them in the molecule)

The Molar mass of O = 16.00 g/mol

If you are confused on where I found them. Let me enlighten you! I found them from a periodic table of elements. 

Add those two values together to get a total molecular molar mass of: 
38.99g/mol 

2.5mol Na2O * ( 38.99 gNa2O / 1 molNa2O) = 97 gNa2O

Mass of Na₂O= 155 g

Given:

Number of moles= 2.5 moles

To find:

Mass of Na₂O= ?

Now, Molar mass of Na₂O can be calculated as:

2* (Molar mass of Na) + Molar mass of O = \(2* 23 +16=46+16=62 \text{g/mol}\)

Molar mass of Na₂O = 62 g/mol

\(\text{Number of Moles}=\frac{\text{Mass}}{\text{Molar mass}}\)

Now, on substituting the values in the above formula:

\(\text{Mass}= \text{Number of moles}* \text{Molar mass}\\\\\text{Mass}= 2.5*62=155 g\)

Mass of Na₂O= 155 g

Learn more:

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