JAMB Chemistry Past Questions & Answers - Page 82

406.

A sample of orange juice is found to have a PH of 3.80. What is the concentration of the hydroxide ion in the juice?

A.

1.6 \(\times\) 10-4

B.

6.3 \(\times\) 10-11

C.

6.3 \(\times\) 10-4

D.

1.6 \(\times\) 10-11

Correct answer is B

PH = - Log[ H+ ]

PH + POH =14

POH = 14 - 3.8

POH = 10.2

POH = - Log[ OH- ]

10.2 = - Log[ OH- ]

10-10.2 = [ OH- ]

[ OH- ] = 6.3 x 10-11

407.

When few drops of concentrated trioxonitrate(V) acid is added to an unknown sample and wanned an intense yellow colouration is observed. The likely functional group present in the sample is

A.

NH2RCHCOOH

B.

CHO

C.

CO

D.

CNH2

Correct answer is A

Xanthopreitic test for the presence of protein, when conc nitric acid is added to the drop, an intense yellow colouration is observed.

It contains all the functional group of protein which includes the amino, alkanol and the carboxylic group. Adding few drops of conc HNO3 to a protein, gives an intense yellow colouration.

It is called Xanthopreitic test.

408.

An isomer of C5H12 is

A.

2–ethyl butane

B.

butane

C.

2–methyl butane

D.

2–methyl propane

Correct answer is C

C5H12 has 5 carbons acid 12 hydrogens.

2–methyl butane

No of carbon=5

No of hydrogen=12

409.

The oxidation number of iodine in KIO3 is

A.

+7

B.

+3

C.

+5

D.

+6

Correct answer is C

If the rules are followed, it is non-negotiable that +5 is the suitable answer to the question.

410.

A given mass of gas occupies 2dm3 at 300k. At what temperature will its volume be doubled, keeping the pressure constant?

A.

400k

B.

480k

C.

550k

D.

600k

Correct answer is D

At constant pressure connotes Charle's law

\(\frac{V_1}{T_1}\) = \(\frac{V_2}{T_2}\)

\(\frac{2dm^3}{300k}\) = 2 x \(\frac{2dm^3}{T_2}\)

T2= 600k