Page 48 - Chemistry - XI

Q12. Name the indicator used in titration of oxalic acid vs NaOH.
Ans. Phenolphthalein

Q13. What is molarity?
Ans. Molarity is defi ned as the number of moles of solute dissolved per litre of solution.
Q14. Why is acid taken in a burette in titration of HCl vs Na CO ?
2
3
Ans. It is easier to detect yellow to pink.
Q15. What is meant by concordant reading?
Ans. Volume of acid used remaining the same, i.e. diff erence in fi nal and initial reading should be same.

Q16. Is NaOH a primary standard? Give reason.
Ans. NaOH is not a primary standard as it cannot be weighed accurately as it is hygroscopic in nature.

Q17. Name two primary standard substances.
Ans. Oxalic acid, Sodium carbonate

Q18. What is end point?
Ans. It is a stage at which acid and base neutralise completely.

Q19. Name the indicator used for titration of a strong acid and a weak base.
Ans. Methyl orange

Q20. How can we minimise titration error?
Ans. Suitable indicator and experimental conductance can reduce titration error.
Q21. Which indicator is used in titration of Na CO against HCl and what is the colour change at
3
2
the end point?
Ans. Methyl orange is used. End Point. Yellow to pink (HCl is taken in a burette)
Q22. How will you prepare 250 mL of 0.05 M solution of Na CO ?
2 3
106 × 0.05 5.3
Ans. Weigh = = 1.325 g of Na CO in 250 mL of solution.
4 4 2 3

COMPETENCY BASED QUESTIONS

Multiple Choice Questions

Q1. What volume of 10.6 gL aqueous solution of Na CO will be required to react with 25 mL of
–1
3
2
M/10 H SO ?
2 4
(a) 23.6 mL (b) 25 mL (c) 35.6 mL (d) 50 mL
Q2. 30 mL of 1 M aqueous solution of NaOH is required to exactly neutralise 25 mL of H SO . The
2
4
conc. of H SO is
2 4
(a) 12 M (b) 0.833 M (c) 0.600 M (d) 0.5 M

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