The s-Block Elements Test 34

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The s-Block Elements Test 34

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Question 1
1 / -0

$$CaCl_2$$ is preferred over $$NaCl$$ for clearing ice on roads on particularly in very cold countries. This is because:

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

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

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

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

Solution

$$CaCl_2$$ is preferred over $$NaCl$$ for clearing ice on roads on particularly in very cold countries due to much lower freezing point of eutectic mixture of $$CaCl_2/H_2O$$.
Question 2
1 / -0

What volume of hydrogen gas at 273 K and 1 atm pressure will be consumed in obtaining 21.6 g of elemental boron (atomic mass = 10.8) form the reduction of boron trichloride by hydrogen:

A
89.6 L

B
67.2 L

C
44.8 L

D
22.4 L

Solution

Hence,option B is correct.
Question 3
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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.

...view full instructions

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

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

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

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

D
None of these

Solution

Lithium only forms monoxide when heated in oxygen. Sodium forms monoxide and peroxide in excess of oxygen.
They do not form stable superoxide.
Thus, M can not be Li and Na.
Question 4
1 / -0

X Y
Liquid sodium metal Breathing apparatus submarine
Potassium Explosive
Potassium nitrate Coolant in nuclear reaction
Potassium superoxide Soft soap
Match the compounds/metal in(X) with their used in (Y). hence correct order is.

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

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

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

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

Solution

Liquid sodium is used as coolants.
Potassium stearate is used as a surface active agent and fiber softener.
Major uses of potassium nitrate are in fertilizers, rocket propellants and fireworks.
potassium superoxide is used as an oxygen source in chemical oxygen generators, such as those used on the space shuttle and on submarines.
Question 5
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The correct increasing order of basic nature among Be, Mg, Ca and Sr is :

A
$$Be < Ca < Mg < Sr$$

B
$$Be < Mg < Sr < Ca$$

C
$$Be < Mg < Ca < Sr$$

D
$$Ca < Sr < Be < Mg$$

Solution

The correct increasing order of basic nature among Be, Mg, Ca and Sr is $$Be < Mg < Ca < Sr$$.
$$Be$$ forms amphoteric oxides and hydroxides, whereas other alkaline earth metals form basic oxides and hydroxides. The basicity increases on moving down the group due to increase in the size of the metal ion, decrease in the ionization energy and increase in the electropositive character. This increases the polarity of metal oxygen bond and internuclear distance which in turn increases the ease of formation of ion and the basic character.
Question 6
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Which one of the following is correct with respect to molar ionic conductance of ions in aqueous solution?

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

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

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

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

Solution

Larger is the size of the ion, smaller is the degree of hydration and larger is the molar ionic conductance. Hence, the correct order of the molar ionic conductance is $$Li^{+}\, <\, Na^{+}\, <\, K^{+}\, <\, Rb^{+}$$.
Question 7
1 / -0

The correct increasing order of melting point of alkali metal carbonates is:

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

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

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

D
None of these

Solution

The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point, the solid and liquid phases exist in equilibrium.

The melting point of carbonates of a particular group increases due to an increase in atomic size. This increases the Van der Waal attraction, which requires more heat to melt.

Li, Na, K, Rb, Cs are IA group elements, the melting point increases from Li to Cs.
The correct order of melting point of carbonates of IA group elements is:

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

Hence, option (B) is correct.

Question 8

1 / -0

Directions For Questions

Reduction potentials of group 1 (alkali metals) are given below :

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

...view full instructions

$$Li(s)\, \rightarrow\, Li^{+}(aq)\, +\, e^{-}$$ involved :

sublimation

ionization

hydration

all of these

Solution

Question 9
1 / -0

Ripening of fruits can be caried out in presence of :

A
$$Na_2SO_4$$

B
$$NaCl$$

C
$$CaCl_2$$

D
$$CaC_2$$

Solution

$$ \begin{array}{l} \text { Calcium Carbide }\left(\mathrm{CaC}_{2}\right) \text { can be used in ripening fruits. } \\ \text { It produces acetylene gas when it comes in contact with moisture } \\ \text { and acetylene gas accelerates the ripening process. } \end{array} $$
Question 10
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Select correct statement(s).

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

B
Mg is present in chlorophyll of green plants.

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

D
All the above are correct statements

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

The s-Block Elements Test 34

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The s-Block Elements Test 34

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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

Solution

Question 2

89.6 L

67.2 L

44.8 L

22.4 L

Solution

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

Solution

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

Solution

Question 5

$$Be < Ca < Mg < Sr$$

$$Be < Mg < Sr < Ca$$

$$Be < Mg < Ca < Sr$$

$$Ca < Sr < Be < Mg$$

Solution

Question 6

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

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

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

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

Solution

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

Solution

Question 8

sublimation

ionization

hydration

all of these

Solution

Question 9

$$Na_2SO_4$$

$$NaCl$$

$$CaCl_2$$

$$CaC_2$$

Solution

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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