Question

1. Assuming one equivalent of NaBH4 can reduce 4 equivalents of carbonyl functional groups, calculate the minimum amount of NaBH4 required to fully reduce 0.35 mmol of Benzil. Indicate if the the NaBH4 or the carbonyl group containing starting material is the limiting reagent.

Answer 1

Answer: Amount of
`NaBH_4` required will be 66.2025 g

Step-by-step explanation:

We are given:

1 equivalent of
`NaBH_4` can reduce 4 equivalents of carbonyl functional groups.

Benzil has 2 carbonyl functional groups. Thus, 1 equivalent of
`NaBH_4` will reduce 2 equivalents of benzil.

Moles of Benzil given = 0.35 mmol =
`3.5* 10^(-4)mol` (Conversion factor: 1 mol = 1000 mmol)

By Stoichiometry:

2 moles of benzil reacts with 1 mole of
`NaBH_4`

So,
`3.5* 10^(-4)mol` of benzil will react with =
`(1)/(2)* 3.5* 10^(-4)=1.75* 10^(-4)mol` of
`NaBH_4`

To calculate the mass of
`NaBH_4`, we use the equation:

`\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}`

Moles of
`NaBH_4=1.75* 10^(-4)mol`

Molar mass of
`NaBH_4` = 37.83 g/mol

Putting values in above equation, we get:

`1.75* 10^(-4)mol=\frac{\text{Mass of }NaBH_4}{37.83g/mol}\\\\\text{Mass of }NaBH_4=66.2025g`

Hence, amount of
`NaBH_4` required will be 66.2025 g