Question

How many molecules of glycine , C2H5O2N are in 1.332 g of glycine?

Answer 1

Step 1 - Remembering the molar mass of glycine and relating it to the number of molecules

Remember the molar mass of glycine is 75.05 g/mol. In our previous session, we have discussed its meaning: one mole of glycine weights 75.05 g.

One mole also represents a specific quantity: 6.02*10^23 unities of something. Since we're talking glycine (a molecule), one mole of glycine represents 6.02*10^23 molecules of glycine.

Therefore, we can say that 6.02*10^23 molecules of glycine (1 mole) weights 75.05 g.

Step 2 - Finding the number of molecules

Since we know the weight of 6.02*10^23 glycine molecules, we can now set the following proportion:

`\begin{gathered} 6.02*10^(23)\text{ glycine molecules weight --- 75.05 g} \\ x\text{ glycine molecules weight --------- 1.332 g} \\ \\ x=(1.332*6.02)/(75.05)*10^(23) \end{gathered}`

Working out the math:

`x=0.106*10^(23)=1.06*10^(22)\text{ molecules of glycine}`

There are thus 1.06*10^22 molecules of glycine in 1.332 g of it.