WAEC Chemistry Past Questions & Answers

441.

Flow of current in electrolytes is due to the movement of

electrons

Holes and electron

Ions

Charges

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Correct answer is C

No explanation has been provided for this answer.

442.

Cathode rays cause an object placed behind a perforated anode to cast a shadow on the screen. This observation shows that the rays

are positively charged

are negatively charged

Have mass

travel in straight lines

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Correct answer is D

Rays travels in straight lines and finds its way through any opening available. It could be refracted, reflected or transmitted based on any obstacle. Option A,B,C are not the reason why the cathode are coasted shadows

443.

An elements used in production of matches is

nitrogen

aluminum

copper

sulphur

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Correct answer is D

Sulphur is an element that burns with a strongly explosive smell, as a result it is explosive smell

444.

Which of the noble gases has the greatest ionization energy

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Correct answer is A

Ionization energy: The amount of energy required to remove an electron from an isolated atom or molecule.

Trends down group :

Ionization energy decreases down the group.
This is due to the shielding or screen effect of the outer electrons from the nucleus.
The attraction is weaker and they are more easily removed.
Helium and radon both belong to group 8 which are called noble gases.
Helium (He) has the highest ionization energy and Radon (Rn) has the lowest ionization energy.