The nitrogen content of a .2476 g sample of a protein was determined by the Kjeldahl method. The NH3 produced with the whoosh was distilled into exactly 50.00mL of HCl in the receiving flask, which was in excess of the amount required to capture the ammonia gas. The excess HCl that was left over required 32.76 mL of .1234 M NaOH for neutralization.

Question

The nitrogen content of a .2476 g sample of a protein was determined by the Kjeldahl method. The NH3 produced with the whoosh was distilled into exactly 50.00mL of HCl in the receiving flask, which was in excess of the amount required to capture the ammonia gas. The excess HCl that was left over required 32.76 mL of .1234 M NaOH for neutralization.

In a preliminary lab, the HCl in the receiving flask had been previously standardized by neutralizing exactly 25.00mL of it with 21.15 mL of the same .1234 M NaOH.

What was the weight % nitrogen in the protein sample?

Answer 1

See your other post above.

Answer 2

To find the weight percentage of nitrogen in the protein sample, we need to follow a series of steps:

1. Calculate the molarity of the HCl solution used to capture the ammonia gas. This can be done using the neutralization reaction between HCl and NaOH:
HCl + NaOH -> NaCl + H2O

From the information provided, we know that 21.15 mL of 0.1234 M NaOH was required to neutralize 25.00 mL of HCl. Therefore, the molarity of the HCl solution is:

M1 * V1 = M2 * V2
(0.1234 M) * (21.15 mL) = M2 * (25.00 mL)
M2 = (0.1234 M * 21.15 mL) / (25.00 mL)
M2 = 0.104796 M

2. Calculate the amount (in moles) of NaOH used to neutralize the excess HCl in the receiving flask:
Moles of NaOH = Molarity * Volume
Moles of NaOH = 0.104796 M * 32.76 mL * (1 L / 1000 mL)
Moles of NaOH = 0.003440 mol

3. Calculate the moles of HCl that were initially present in the receiving flask, based on the neutralization reaction:
Moles of HCl = Moles of NaOH
Moles of HCl = 0.003440 mol

4. Calculate the moles of ammonia gas produced, assuming that 1 mole of ammonia produces 1 mole of HCl:
Moles of NH3 = Moles of HCl
Moles of NH3 = 0.003440 mol

5. Determine the moles of nitrogen in the protein sample, using the fact that 1 mole of ammonia contains 1 mole of nitrogen:
Moles of nitrogen = Moles of NH3
Moles of nitrogen = 0.003440 mol

6. Finally, calculate the weight percentage of nitrogen in the protein sample by dividing the weight of nitrogen by the weight of the entire protein sample and multiplying by 100:
Weight % nitrogen = (Moles of nitrogen / Weight of protein sample) * 100

However, we don't have the weight of the protein sample provided in the information given. To calculate the weight percentage of nitrogen, we need the weight of the protein sample as well.