JAMB Chemistry Past Questions & Answers - Page 164

816.

Beryllium and aluminum have similar properties because they?

A.

are both metals

B.

belong to the same group

C.

belong to the same period

D.

are positioned diagonally to each other

Correct answer is D

At the beginning of periods 2 and 3 of the Periodic Table, there are several cases where an element at the top of one group has some similarities with an element in the next group. For example, boron is a non-metal with some properties rather like silicon. Unlike the rest of Group 2, beryllium has some properties resembling aluminium. And lithium has some properties which differ from the other elements in Group 1, and in some ways resembles magnesium. There is said to be a diagonal relationship between these elements. There are several reasons for this, but each depends on the way atomic properties like electronegativity vary around the Periodic Table.

817.

An element X has electron configuration 1s2 2s2 2p6 3s2 3p5. Which of the following statements is correct about the element?

A.

lt has a completely filled p-orbital

B.

lt has 5 electrons in its outermost shell.

C.

lt belongs to group ll on the periodic table

D.

lt is a halogen

Correct answer is D

No explanation has been provided for this answer.

818.

200 cm3 of a gas at 25oC exerts a pressure of 700 mmHg. Calculate its pressure if its volume increase 350 cm3 at 75oC.

A.

342.53 mmHg

B.

1430.54 mmHg

C.

467.11 mmHg

D.

400.00 mmHg

Correct answer is C

\(\frac{p 1V 1}T 1\) = \(\frac{P 2V 2}{T 2}\) \(\frac{700x200}{298}\) = \(\frac{P2X 350}{348}\) P2 = \(\frac{700x200x348}{298x350}\) = 467.11mmHg

819.

A gas X diffuses twice as fast as gas Y. if the relative molecular mass of X is 32, calculate the relative molecular mass of Y.

A.

128

B.

8

C.

16

D.

64

Correct answer is A

\(\frac{RY}{RX}\) = \(\frac{\sqrt{My}}{\sqrt{My}}\) 1/2 = \(\frac{\sqrt{32}}{\sqrt{y}}\) \(\frac{32}{y}\) = 1/4
Y = \(\frac{32x4}{1}\) = 128

820.

What is the percentage of sulphur in sulphur (IV) oxide?

A.

66%

B.

25%

C.

40%

D.

50%

Correct answer is D

molar mass of SO 2=64 :.%S=32/64 x 100 = 50%