The s-Block Elements Test 34

Directions For Questions

Lithium only forms monoxide when heated in oxygen. Sodium forms monoxide and peroxide in excess of oxygen. Other alkali metals from superoxide with oxygen, i.e., $$MO_2$$. The abnormal behavior of lithium is due to small size. The larger size of higher alkali metals also decides the role in formation of superoxides. All the three anions abstract proton from water. The three anions are related to each other as follows:

$${O_2}^- \xrightarrow{\frac{1}{2}O_2} {O_2}^{2-} \xrightarrow{O_2} 2{O_2}^-$$

Oxide ion $$\rightarrow $$ Peroxide ion $$\rightarrow $$ Superoxide ion.

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Consider the following reaction:
$$M+O_2 \rightarrow MO_2$$
$$M$$ is an alkali metal$$MO_2$$ is a stable superoxide

X	Y
Liquid sodium metal	Breathing apparatus submarine
Potassium	Explosive
Potassium nitrate	Coolant in nuclear reaction
Potassium superoxide	Soft soap

Element	$$E^0(U)$$
$$Li^++e^- \rightarrow Li$$	-3.045
$$Na^++e^- \rightarrow Na$$	-2.714
$$K^++e^- \rightarrow K$$	-2.925
$$Rb^++e^- \rightarrow Rb$$	-2.925
$$Cs^++e^- \rightarrow Cs$$	-2.923

The s-Block Ele...

Question 1

$$CaCl_2$$ is not soluble in $$H_2O$$ than $$NaCl$$

$$CaCl_2$$ is hygroscopic but $$NaCl$$ is not

eutectic mixture of $$CaCl_2$$/$$H_2O$$ freezes at $$-55^oC$$ while that of $$NaCl$$/$$H_2O$$ freezes at $$-18^oC$$

$$NaCl$$ makes the road slippery but $$CaCl_2$$ does not

Question 2

89.6 L

67.2 L

44.8 L

22.4 L

Question 3

$$M$$ can not be $$Li$$ and $$Na$$

$$M$$ can not be $$Cs$$ and $$Rb$$

$$M$$ can not be $$Li$$ and $$Rb$$

None of these

Question 4

A-I, B-III, C-II, D-IV

A-III, B-IV, C-II, D-I

A-II, B-I, C-III, D-IV

A-IV, B-II, C-III, D-I

Question 5

$$Be < Ca < Mg < Sr$$

$$Be < Mg < Sr < Ca$$

$$Be < Mg < Ca < Sr$$

$$Ca < Sr < Be < Mg$$

Question 6

$$Li^{+}\, <\, Na^{+}\, <\, K^{+}\, <\, Rb^{+}$$

$$Rb^{+}\, <\, K^{+}\, <\, Na^{+}\, <\, Li^{+}$$

$$Sr^{2+}\, <\, Ca^{2+}\, <\, Mg^{2+}\, <\, Be^{2+}$$

$$Na^{+}\, <\, K^{+}\, <\, Li^{+}\, <\, Rb^{+}$$

Question 7

$$Cs_2CO_3\, <\, Na_2CO_3\, <\, K_2CO_3\, <\, Rb_2CO_3\, <\, Li_2CO_3$$

$$Li_2CO_3\, <\, Na_2CO_3\, <\, K_2CO_3\, <\, Rb_2CO_3\, <\, Cs_2CO_3$$

$$Li_2CO_3\, <\, Rb_2CO_3\, <\, K_2CO_3\, <\, Na_2CO_3\, <\, Cs_2CO_3$$

None of these

Question 8

sublimation

ionization

hydration

all of these

Question 9

$$Na_2SO_4$$

$$NaCl$$

$$CaCl_2$$

$$CaC_2$$

Question 10

$$Mg^{2+}$$ ions are necessary for the activation of phosphate transfer enzymes.

Mg is present in chlorophyll of green plants.

Mg is present in chlorophyll used in photosynthesis in green plants.

All the above are correct statements

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