Question

9. if you use 10 g of benzil to react with enough amount of acetic nabh4, how much product (benzoin) will you obtain if the reaction yield is 85%?

Answer 1

Answer : The mass of benzoin is, 8.58 grams.

Explanation :

First we have to calculate the moles of benzil.

`\text{Moles of benzil}=\frac{\text{Mass of benzil}}{\text{Molar mass of benzil}}`

Molar mass of benzil = 210.23 g/mol

`\text{Moles of benzil}=(10g)/(210.23g/mol)=0.0476mol`

Now we have to calculate the moles of benzoin.

The balanced chemical reaction is:

`(C_6H_5CO)_2+NaBH_4\rightarrow C_(14)H_(12)O_2+BH_3+NaOH`

From the balanced chemical reaction we conclude that,

As, 1 mole of benzil react to give 1 mole of benzoin

So, 0.0476 mole of benzil react to give 0.0476 mole of benzoin

Now we have to calculate the mass of benzoin.

`\text{Mass of benzoin}=\text{Moles of benzoin}* \text{Molar mass of benzoin}`

Molar mass of benzoin = 212.24 g/mol

`\text{Mass of benzoin}=0.0476mol* 212.24g/mol=10.1g`

Theoretical yield of benzoin = 10.1 g

Now we have to calculate the experimental mass of benzoin.

`\% \text{ yield of reaction}=\frac{\text{ Experimental yield of benzoin}}{\text{ Theoretical yield of benzoin}}* 100`

`\text{Experimental yield of benzoin}=(85)/(100)* 10.1g=8.58g`

Therefore, the mass of benzoin is, 8.58 grams.