The S-Block Elements NDA Questions

NDA Chemistry

The S-Block Elements MCQ Questions


13.
As we move down Group 1, the melting and boiling points of the alkali metals generally:
A.
Increase
B.
First decrease then increase
C.
Remain constant
D.
Decrease
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ANSWER :
D. Decrease
14.
Alkali metals impart characteristic colours to a flame. What colour does a sodium salt impart to the flame?
A.
Brick red
B.
Lilac (violet)
C.
Golden yellow
D.
Crimson red
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ANSWER :
C. Golden yellow
15.
What flame colour is imparted by lithium salts?
A.
Golden yellow
B.
Lilac (violet)
C.
Apple green
D.
Crimson red
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ANSWER :
D. Crimson red
16.
What flame colour is imparted by potassium salts?
A.
Crimson red
B.
Brick red
C.
Lilac (violet)
D.
Golden yellow
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ANSWER :
C. Lilac (violet)
17.
Alkali metals and their salts impart characteristic colours to a flame because:
A.
The salts decompose to release coloured gases
B.
The heat excites the outer electron, which emits energy as visible light on returning to the ground state
C.
The metal atoms burn completely in the flame
D.
The flame reacts chemically with the metal ions
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ANSWER :
B. The heat excites the outer electron, which emits energy as visible light on returning to the ground state
18.
Which of the following alkali metals shows photoelectric effect, i.e., loses electrons when exposed to light, and is therefore used in photoelectric cells?
A.
Caesium
B.
Potassium
C.
Lithium
D.
Sodium
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ANSWER :
A. Caesium