Question

If you are reacting 4.00 g benzophenone (MM = 182.22 g/mol) and you want to add 1.5 equivalents of NaBH4(MM = 37.83 g/mol), what is the minimum volume (in mL) of 2.0 M HCl you need to add to ensure the reaction is fully quenched?

Answer 1

Ans.

Mass of benzophenone = 4.00g

Molar mass of benzophenone = 182.22g/mol

No. of mol of benzophenone is

1.5 equivalents of NaBH₄ is used.

1 equivalents correspond to 0.02195 mol of benzophenone.

Therefore, 1.5 equivalents of NaBH₄ is

of NaBH₄

However, 1 equivalent of benzophenone uses only 0.25 equivalents of NaBH₄

(since 0.02195 mol of benzophenone is taken)

of NaBH₄

Theefore, excess NaBH₄ is

Molarity of HCl = 2.0M

It means there are 2 mol of HCl is present in 1L (1000mL) of the HCl solution.

1000mL HCl solution has 2 mol of HCl

Therefore, 500mL HCl solution has 1 mol of HCl.

0.02744 mol will be present in

Therefore, the minimum volume of HCl that need to be added to ensure the reaction is quenched is 14.0 mL

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