41. The properties of lithium are similar to those of $$Mg.$$ This is because
A
both have nearly the same size
B
the ratio of their charge to size is nearly the same
C
both have similar electronic configurations
D
both are found together in nature
Answer :
the ratio of their charge to size is nearly the same
42. What happens when $${H_2}$$ is passed over lithium at $$1073\,K?$$
A
Covalent lithium hydride is formed.
B
Coloured complex is formed.
C
Ionic lithium hydride is formed.
D
No reaction takes place.
Answer :
Ionic lithium hydride is formed.
43. The reducing power of a metal depends on various factors. Suggest the factor which makes $$Li,$$ the strongest reducing agent in aqueous solution.
A
Sublimation enthalpy
B
Ionisation enthalpy
C
Hydration enthalpy
D
Electron - gain enthalpy
Answer :
Hydration enthalpy
44. The metallic lustre exhibited by sodium is explained by
A
diffusion of sodium ions
B
oscillation of loose electrons
C
excitation of free protons
D
existence of body centered cubic lattice
Answer :
oscillation of loose electrons
45. $$Be{F_2}$$ is soluble in water whereas fluorides of other alkaline earth metals are insoluble because of
A
ionic nature of $$Be{F_2}.$$
B
covalent nature of $$Be{F_2}.$$
C
greater hydration energy of $$B{e^{2 + }}\,ion$$ as compared to its lattice energy.
D
none of these.
Answer :
greater hydration energy of $$B{e^{2 + }}\,ion$$ as compared to its lattice energy.
46. Two metals $$(A)$$ and $$(B)$$ belong to the same group of the periodic table. Metal $$(A)$$ forms an insoluble oxide but a soluble sulphate, metal $$(B)$$ forms a soluble oxide but an insoluble sulphate. Both metals $$(A)$$ and $$(B)$$ form hydroxides which are soluble in alkalis. $$(A)$$ and $$(B)$$ are
A
$$Ba\,{\text{and}}\,Mg$$
B
$$Na\,{\text{and}}\,K$$
C
$$Mg\,{\text{and}}\,Ba$$
D
$$K\,{\text{and}}\,Rb$$
Answer :
$$Mg\,{\text{and}}\,Ba$$
47. The main oxides formed on combustion of $$Li,Na$$ and $$K$$ in excess of air are, respectively :
A
$$L{i_2}{O_2},\,N{a_2}{O_2}\,{\text{and}}\,K{O_2}$$
B
$$L{i_2}O,N{a_2}{O_2}\,{\text{and}}\,K{O_2}$$
C
$$L{i_2}O,\,N{a_2}O\,\,{\text{and}}\,K{O_2}$$
D
$$Li{O_2},N{a_2}{O_2}\,{\text{and}}\,{K_2}O$$
Answer :
$$L{i_2}O,N{a_2}{O_2}\,{\text{and}}\,K{O_2}$$
48.
“Metals are usually not found as nitrates in their ores”.
Out of the following two ( I and II ) reasons which is/are true for the above observation ?
I. Metal nitrates are highly unstable.
II. Metal nitrates are highly soluble in water.
A
I and II are true
B
I and II are false
C
I is false but II is true
D
I is true but II is false
Answer :
I is false but II is true
49. Which of the following statements about $$N{a_2}{O_2}$$ is not correct ?
A
It is diamagnetic in nature
B
It is derivative of $${H_2}{O_2}$$
C
$$N{a_2}{O_2}$$ oxidises $$C{r^{3 + }}$$ to $$CrO_4^{2 - }$$ in acid medium.
D
It is the super oxide of sodium
Answer :
It is the super oxide of sodium
50. What is the formula of hydrated $$BeC{l_2}?$$
A
$$BeC{l_2} \cdot {H_2}O$$
B
$$BeC{l_2} \cdot 2{H_2}O$$
C
$$BeC{l_2} \cdot 3{H_2}O$$
D
$$BeC{l_2} \cdot 4{H_2}O$$
Answer :
$$BeC{l_2} \cdot 4{H_2}O$$