NCERT Class 12 Chemistry Entrance Exams Questions and Answers

NCERT Class 12 Chemistry Entrance Exams Questions & Answers NCERT Class 12 Chemistry QUESTIONS

NCERT Class 12 Chemistry Entrance Exams Questions and Answers

71 The half life of the first order reaction having rate constant K = 1.7 x 10-5s-1 is
A 11.3 h
B 1.8 h
C 12.1 h
D 9.7 h

Answer: 11.3 h
72 For a chemical reaction A→B, it is found that the rate of reaction doubles when the concentration of A is increased four times. The order of reaction is
A Zero
B Half
C Two
D One

Answer: Half
73 Which of the following aqueous solutions should have the highest boiling point?
A 1.0 M NaOH
B 1.0 M Na2SO4
C 1.0 M NH4NO3
D 1.0 M KNO3

Answer: 1.0 M Na2SO4
74 Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult’s law?
A Methanol and acetone.
B Phenol and aniline.
C Chloroform and acetone.
D Nitric acid and water.

Answer: Methanol and acetone.
75 Which of the following acids is a vitamin?
A Ascorbic acid
B Adipic acid
C Aspartic acid
D Saccharic acid

Answer: Ascorbic acid
76 Each polypeptide in a protein has aminoacids linked with each other in a specific sequence. This sequence of amino acids is said to be __________ .
A primary structure of proteins.
B secondary structure of proteins.
C tertiary structure of proteins.
D quaternary structure of proteins.

Answer: primary structure of proteins.
77 Which of the following reactions of glucose can be explained only by its cyclic structure? [NCERT Exemplar]
A Pentaacetate of glucose does not react with hydroxylamine.
B Glucose is oxidised by nitric acid to gluconic acid.
C Glucose forms pentaacetate.
D Glucose reacts with hydroxylamine to form an oxime.

Answer: Pentaacetate of glucose does not react with hydroxylamine.
78 Low concentration of oxygen in the blood and tissues of people living at high altitude is due to _________ .
A low temperature
B low atmospheric pressure
C high atmospheric pressure
D both low temperature and high atmospheric pressure

Answer: low atmospheric pressure
79 Activation energy of a chemical reaction can be determined by __________ .
A determining the rate constant at standard temperature.
B determining the rate constants at two temperatures.
C determining probability of collision.
D using catalyst.

Answer: determining the rate constants at two temperatures.
80 A first order reaction is 50% completed in 1.26 × 1014 s. How much time would it take for 100% completion?
A infinite
B 1.26 × 1015 s
C 2.52 × 1014 s
D 2.52 × 1028 s

Answer: infinite

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