Question

6. The Kjeldahl method is commonly used to determine the percent protein in meat products. The majority of protein molecules in living matter contain just about 16% nitrogen (N). A 1.250 g of meat sample is heated with concentrated sulfuric acid and a catalyst to convert all the nitrogen (N) in the meat to (NH4)2SO4. Then excess NaOH(aq) is added to the mixture, which is heated to expel ammonia gas (NH3(g)). All the nitrogen, in the form of NH3(g), from the meat sample is absorbed in and neutralized by 50.00 mL of dilute sulfuric acid 0.2 M H2SO4 (aq) (eq.1). The excess H2SO4 (aq) requires 32.24 mL of 0.4498 M NaOH for its titration (eq. 2). 2NH3(g) (N from meat) + H2SO4(aq) ? (NH4)2SO4(aq) (eq.1) H2SO4(aq) + 2NaOH(aq) ? Na2SO4(aq) + 2H2O(l) (eq.2) (a) Calculate the no. of moles (mol) of the excess amount of H2SO4(aq) from the titration with NaOH(aq) (eq.2). [3 marks] (b) Calculate the no. of moles (mol) of H2SO4(aq) consumed in the neutralization of ammonia gas (NH3(g)). [2 marks] (c) Determine the mass (g) of N in NH3(g) (from eq. 1) and thus the mass (g) of protein in the meat sample. [4 marks] (d) Determine the percent of protein (by mass) in the meat sample (%w/w). [3 marks]

          6. The Kjeldahl method is commonly used to determine the percent protein in meat products. The majority of protein molecules in living matter contain just about 16% nitrogen (N).

A 1.250 g of meat sample is heated with concentrated sulfuric acid and a catalyst to convert all the nitrogen (N) in the meat to (NH4)2SO4. Then excess NaOH(aq) is added to the mixture, which is heated to expel ammonia gas (NH3(g)). All the nitrogen, in the form of NH3(g), from the meat sample is absorbed in and neutralized by 50.00 mL of dilute sulfuric acid 0.2 M H2SO4 (aq) (eq.1). The excess H2SO4 (aq) requires 32.24 mL of 0.4498 M NaOH for its titration (eq. 2).

2NH3(g) (N from meat) + H2SO4(aq) ? (NH4)2SO4(aq) (eq.1)
H2SO4(aq) + 2NaOH(aq) ? Na2SO4(aq) + 2H2O(l) (eq.2)

(a) Calculate the no. of moles (mol) of the excess amount of H2SO4(aq) from the titration with NaOH(aq) (eq.2). [3 marks]
(b) Calculate the no. of moles (mol) of H2SO4(aq) consumed in the neutralization of ammonia gas (NH3(g)). [2 marks]
(c) Determine the mass (g) of N in NH3(g) (from eq. 1) and thus the mass (g) of protein in the meat sample. [4 marks]
(d) Determine the percent of protein (by mass) in the meat sample (%w/w). [3 marks]

6. The Kjeldahl method is commonly used to determine the percent protein in meat products. The majority of protein molecules in living matter contain just about 16% nitrogen (N).

A 1.250 g of meat sample is heated with concentrated sulfuric acid and a catalyst to convert all the nitrogen (N) in the meat to (NH4)2SO4. Then excess NaOH(aq) is added to the mixture, which is heated to expel ammonia gas (NH3(g)). All the nitrogen, in the form of NH3(g), from the meat sample is absorbed in and neutralized by 50.00 mL of dilute sulfuric acid 0.2 M H2SO4 (aq) (eq.1). The excess H2SO4 (aq) requires 32.24 mL of 0.4498 M NaOH for its titration (eq. 2).

2NH3(g) (N from meat) + H2SO4(aq) ? (NH4)2SO4(aq) (eq.1)
H2SO4(aq) + 2NaOH(aq) ? Na2SO4(aq) + 2H2O(l) (eq.2)

(a) Calculate the no. of moles (mol) of the excess amount of H2SO4(aq) from the titration with NaOH(aq) (eq.2). [3 marks]
(b) Calculate the no. of moles (mol) of H2SO4(aq) consumed in the neutralization of ammonia gas (NH3(g)). [2 marks]
(c) Determine the mass (g) of N in NH3(g) (from eq. 1) and thus the mass (g) of protein in the meat sample. [4 marks]
(d) Determine the percent of protein (by mass) in the meat sample (%w/w). [3 marks]

Added by Claire J.

Question

Please give Ace some feedback