Question

A first year chemistry laboratory involved the students to perform volumetric analysis of a solution of carbonic acid (H2CO3) of unknown concentration. With a view to determine the concentration of H2CO3, the students have performed volumetric titration with standardised solution of sodium hydroxide. To analyse the acid, 50.00 mL of the unknown acid solution is diluted to 200.00 mL. Then 25.00 mL aliquots of the diluted acid solution were titrated with a 0.3215 molL-1 NaOH solution to the endpoint. The following data were collected by one of the group during the volumetric runs of the diluted H2CO3 solution. Titration #1 volume: 24.90 mL Titration #2 volume: 25.55 mL Titration #3 volume: 24.75 mL Titration #4 volume: 24.80 mL Answer following parts of this question using above data: (a). What is the average titre volume in this titration? (2 mark) (b). Determine the number of moles of H2CO3 in the 25.00 mL aliquots (note: 1 mole of H2CO3 reacts with 2 moles of NaOH). (4 marks) (c). How many moles of H2CO3 were in the 200.0 mL of diluted acid solution? (2 mark) (d). Using your answer from (c), calculate the mass of H2CO3 (molar mass 62.026 gmol-1) in the original, undiluted, acid solution. (3 marks) Show all working including units in each step.

          A first year chemistry laboratory involved the students to
perform volumetric analysis of a solution of carbonic acid (H2CO3)
of unknown concentration. With a view to determine the
concentration of H2CO3, the students have performed volumetric
titration with standardised solution of sodium hydroxide. To
analyse the acid, 50.00 mL of the unknown acid solution is diluted
to 200.00 mL. Then 25.00 mL aliquots of the diluted acid solution
were titrated with a 0.3215 molL-1 NaOH solution to the endpoint.
The following data were collected by one of the group during the
volumetric runs of the diluted H2CO3 solution.
Titration #1 volume: 24.90 mL
Titration #2 volume: 25.55 mL
Titration #3 volume: 24.75 mL
Titration #4 volume: 24.80 mL
Answer following parts of this question using above data:
(a). What is the average titre volume in this titration? (2
mark)
(b). Determine the number of moles of H2CO3 in the 25.00 mL
aliquots (note: 1 mole of H2CO3 reacts with 2 moles of NaOH). (4
marks)
(c). How many moles of H2CO3 were in the 200.0 mL of diluted
acid solution? (2 mark)
(d). Using your answer from (c), calculate the mass of H2CO3
(molar mass 62.026 gmol-1) in the original, undiluted, acid
solution. (3 marks)
Show all working including units in each step.

Added by Philip S.

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