# chemistry

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You need to find the number of moles in 5mL of a substance given the density and the molecular weight.

How do you do this?

• chemistry -

lets take oxygen to be the substance given. the molecular weight also called the molar mass given as 16. the density always remain constant as 1g/ml. so lets comvert everything together as

5ml*1g/ml*1mole/16g = 0.313moles.

remember that 16g/mol is the molarmass or molecular weight.

• chemistry -

The infor by chinomso is good except that the molar mass oxygen is 32 and not 16. Let's use something besides oxygen (especially since it doesn't have a density of 1.0 g/mL.)

H2O can be used and it does have a density of 1.0 g/mL.
So 5 mL x (1.0 g/mL) x (1 mol/18 g) = moles H2O where 18 is the molar mass of H2O.

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