The s-Block Elements Test 23

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The s-Block Elements Test 23

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following elements does not form hydride by direct heating with dihydrogen?

A
Be

B
Mg

C
Sr

D
Ba

Solution

All the elements except beryllium combine with hydrogen upon heating to form their hydrides, $$MH_2$$
$$BeH_2$$, however, can be prepared by the reaction of $$BeCl_2$$ with $$LiAlH_4$$.
$$2BeCl_2 + LiAlH_4 \rightarrow 2BeH_2 + LiCl + AlCl_3$$
Question 2
1 / -0

Which of the following reacts with water at a high rate?

A
Li

B
K

C
Na

D
Rb

Solution

As we move down in a group, reactivity of elements with water increases.
Among the given first group members, Rb is the metal of $$5^{th}$$ period, whereas all others are elements of period lower than 5.

Hence, Option "D" is the correct answer.
Question 3
1 / -0

Which of the following statement(s) is/are CORRECT for $$Be^{+3}$$?

A
It is isoelectronic with $$Li^{+2}$$

B
The value of degeneracy for $$2^{nd}$$ excited state is $$3$$

C
On accepting two electrons, the value of neutron excess with change

D
Number of degenerate orbitals in its $$1^{st}$$ excited state is $$4$$

Solution

$$Be^{+3}$$ is isoelectronic with $$Li^{+2}$$. Both the ions are having 1 electron only in their valence shells. So they are isoelectronic with each other.
So the option A is the correct statement for $$Be^{+3}$$.
Hence option A is correct.
Question 4
1 / -0

Select the correct statement out of the following.

A
calcium fluoride is soluble in water.

B
barium sulfate is soluble in water.

C
barium dioxide is soluble in water.

D
magnesium sulfate is soluble in water.
Solution
- The solubility of a compound depends on the co-relation between lattice enthalpy and hydration enthalpy. If the hydration enthalpy is equal to or greater than the lattice enthalpy, then the salt is water-soluble. More the hydration enthalpy as compared to lattice enthalpy more will be the solubility of salt in water.
- $$MgSO_4$$ is soluble in water but $$BaSO_4$$ is not because of the size of $$Ba^{2+}$$ and $$SO_4^{2-}$$ ions is very large which leads to higher lattice enthalpy than that of hydration enthalpy. Barium hydroxide and barium oxide, are partially soluble in water and Calcium Fluoride is also insoluble due to extremely high lattice energy.
Thus, option D is correct.
Question 5
1 / -0

Which of the following metals can form nitride with nitrogen ?

A
$$Li$$

B
$$Na$$

C
$$Mn$$

D
$$Ca$$

Solution

Lithium is the only alkali metal which combines directly with nitrigen to form lithium nitride.

$$Li_{(s)}+N_{2(g)}\longrightarrow 2Li_3N_{(s)}$$

As lithium is the smallest alkali metal, $$Li^+$$ will have the highest positive charge density.

As nitride $$(N^{3-})$$ ion is an extremely small highly charged anion, it forms stable ionic compound with cations of high positive charge density, i.e. $$Li^{+}$$.
Question 6
1 / -0

Property of the alkaline earth metals that increases with their atomic number is:

A
IE

B
Solubility of their hydroxides

C
Solubility of their sulphates

D
Eletronegativity

Solution

In alkaline earth metals as the atomic number increases the number of atomic orbitals increases. In case of hydroxides, the lattice energies are different because of medium of size of hydroxide ions decreases on moving from $$Be$$ to $$Ba$$.This tend to increase the solubility and to overcome the counter-effect produced by decrease in hydration energy. Hence the solubility of alkaline earth metal hydroxides increases with increase in atomic number.
Whereas electronegativity, Solubility of their sulphates and IE decreases with increase in atomic number.

Hence option B is correct answer.
Question 7
1 / -0

Dark blue solution of alkali earth metal in liq.ammonia produce ____on evaporation of ammonia?

A
metal

B
metal amide

C
$$[M(NH_3)_6]^+$$

D
hexaammoniated metal

Solution

Dark blue solution of alkali earth metal in liquid ammonia produce $$[M(NH_3)_6]^{+}$$ on evaporation of ammonia.
Hence option C is correct answer.
Question 8
1 / -0

Select the incorrect statement:

A
sodium and potassium are $$6$$th and $$7$$th most abundant element in the earth's crust

B
$$NaOH$$ is hygroscopic in nature

C
if a crystal of $$NaOH$$ is exposed to air for longer periods it potassium a white powder of $$Na_{2}CO_{3}$$

D
lithium is an alkali metal and can be used in photoelectric cells

Solution

Among alkali metals, cesium has lowest ionisation enthalpy and hence it can show photoelectric effect to the maximum extent and therefore preffered in photoelectric cell. The alkali metal widely used in photoelectric cell is Cs
Alkali metals have lower ionisation energy than their counterparts and hence havemhigher chance of emitting electrons, when a radiation falls on them. So they are used in photoelectric cells so that they easily emit electron when energy containing photons in sunlight strikes them.
Hence option D is incorrect statement
Question 9
1 / -0

Which elements does not combine directly with nitrogen at high temperature?

A
Li

B
Rb

C
Sr

D
Mg

Solution

Only $$Rb$$ does not combine with $$N_2$$ at high temperature. Because heavier metals like $$Rb$$ are seen to be chemically inactive towards $$N_2$$ upon heating.

Since the nitride ion holds a high formal charge $$(N^{3-})$$ and contains an adverse molar ration of cations to anions $$(3:1)$$

it is impossible to form a stable structure. But alkali metal $$Li$$ can react with $$N_2$$ at room temperature. $$Sr$$ and $$Mg$$ can react with $$N_2$$ at high temperature.

So, the correct option is $$Rb$$
Question 10
1 / -0

The products obtained on heating $$LiNO_3$$ will be

A
$$LiNO_2+O_2$$

B
$$Li_2O+NO_2+O_2$$

C
$$Li_3N+O_2$$

D
$$Li_2O+NO+O_2$$

Solution

$$4LiNO_3 \longrightarrow 2Li_2O +4NO_2+ O_2$$
Lithium nitrate behaves differently from other alkali metal nitrates. Lithium nitrate on thermal decomposition produces metal oxide, $$NO_2$$ and $$O_2$$. While other alkali metal nitrate on heating produces metal nitrite and oxygen.

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The s-Block Elements Test 23

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The s-Block Elements Test 23

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SHARING IS CARING

Question 1

Be

Mg

Sr

Ba

Solution

Question 2

Li

K

Na

Rb

Solution

Question 3

It is isoelectronic with $$Li^{+2}$$

The value of degeneracy for $$2^{nd}$$ excited state is $$3$$

On accepting two electrons, the value of neutron excess with change

Number of degenerate orbitals in its $$1^{st}$$ excited state is $$4$$

Solution

Question 4

calcium fluoride is soluble in water.

barium sulfate is soluble in water.

barium dioxide is soluble in water.

magnesium sulfate is soluble in water.

Solution

Question 5

$$Li$$

$$Na$$

$$Mn$$

$$Ca$$

Solution

Question 6

IE

Solubility of their hydroxides

Solubility of their sulphates

Eletronegativity

Solution

Question 7

metal

metal amide

$$[M(NH_3)_6]^+$$

hexaammoniated metal

Solution

Question 8

sodium and potassium are $$6$$th and $$7$$th most abundant element in the earth's crust

$$NaOH$$ is hygroscopic in nature

if a crystal of $$NaOH$$ is exposed to air for longer periods it potassium a white powder of $$Na_{2}CO_{3}$$

lithium is an alkali metal and can be used in photoelectric cells

Solution

Question 9

Li

Rb

Sr

Mg

Solution

Question 10

$$LiNO_2+O_2$$

$$Li_2O+NO_2+O_2$$

$$Li_3N+O_2$$

$$Li_2O+NO+O_2$$

Solution

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