NECO Past Questions and Answers - Page 188

936.

Which of the following statements about the pressure in a liquid is NOT correct? It

A.

acts in all direction

B.

changes with the material of the container

C.

is the same at all points in the same horizontal plane

D.

varies with the density of the liquid

E.

varies with the depth of the liquid

Correct answer is B

No explanation has been provided for this answer.

937.

Determine the value of x from the nuclear reaction below,

\(^{222}_{86}Rn\) → \(^{x}_{88}Ra\) + 2β + energy

A.

220

B.

222

C.

224

D.

226

E.

228

Correct answer is B

The equation above is Beta-decay:
where β is an electron → \(^{0} _{-1}e\)

2β in the equation = \(^{0} _{-1}e\) + \(^{0} _{-1}e\) →  \(^{0} _{-2}e\)

\(^{222}_{86}Rn\) → \(^{x}_{88}Ra\) + \(^{0} _{-2}e\) + energy

where  \(^{x}_{88}Ra\) + \(^{0} _{-2}e\) → \(^{222}_{86}Rn\)

: x = 222 for element Radon [ \(^{222}_{88}Ra\)

938.

Which of the following substances undergoes sublimation?

A.

Ether

B.

Ice

C.

Iodine

D.

Naphthalene

E.

Turpentine

Correct answer is C

No explanation has been provided for this answer.

939.

The space between the two walls of a vacuum flask is completely evacuated to reduce heat loss by

A.

condensation

B.

conduction

C.

convection

D.

evaporation

E.

radiation

Correct answer is C

No explanation has been provided for this answer.

940.

An observer heard the sound of thunder 5.8s after the lightning flash was seen. How far was he from the source? [Speed of sound in air = 330ms-1]

A.

957m

B.

1914m

C.

3828m

D.

8700m

E.

17400m

Correct answer is B

VELOCITY=DISTANCE/TIME

Distance = 330×5.8 Distance = 1914m