Tag: group 2

Questions Related to group 2

Which of the following metals cannot give flame
tests?

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. Be

  2. Na

  3. K

  4. Ca

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Correct Option: A
Explanation:

Beryllium cannot give flame test. Beryllium has small size. It strongly binds its electrons. Thus it has high ionization enthalpy. The thermal energy of flame is not sufficient to excite its electrons.

Which of the following salt gives a crimson red colour in flame test?

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. $BaCl _{2}$

  2. $CaCl _{2}$

  3. $BeCl _{2}$

  4. $SrCl _{2}$

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Correct Option: D
Explanation:

Strontium chloride($SrCl _2$) gives crimson red colour in the flame test. It is due to the excitation of electrons by the thermal energy, which is then followed by de-excitation of electron to ground state along with liberation of light in the visible range.

Passivity is exhibited by: $A) Be , B) Mg, C) Al ,D) B$

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. $A, B$

  2. $B, C$

  3. $A, C$

  4. $B, D$

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Correct Option: C
Explanation:

Action of oxidizing agents such as conc. nitric acid forms a layer of an oxide on the surface of Be and Al. Hence these metals become passive and do not react.

Sulphate of an alkaline earth metal which crystalizes without water of hydration is?

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. $Be^{2+}$

  2. $Mg^{2+}$

  3. $Ca^{2+}$

  4. $Sr^{2+}$

Show answer
Correct Option: D
Explanation:

Strontium sulphate crystalizes without water of hydration.

Assertion(A) : Beryllium and magnesium do not impart characteristic colour in flame.
Reasoning(R) : Both Beryllium and magnesium have high I.E.

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. Both Assertion and Reason are true and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are true but Reason is not a correct explanation of Assertion

  3. Assertion is true but Reason is false

  4. Both Assertion and Reason are false

Show answer
Correct Option: A
Explanation:

Small sized Be and Mg atoms have high ionization energies. Hence, the energy of flame is not sufficient to excite their electrons. Thus, Be and Mg do not produce colour in flame.

Alkaline earth metal(s) which does (do) not
impart colour to the flame is (are):

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. Be

  2. Mg

  3. Ca

  4. Sr

Show answer
Correct Option: A,B
Explanation:

Beryllium($Be$) and magnesium($Mg$) cannot give flame test. They have small size. They strongly binds their electrons. Thus they have high ionization enthalpies. The thermal energy of flame is not sufficient to excites their electrons.

Which of the following shows least melting point?

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. $Be$

  2. $Mg$

  3. $Ca$

  4. $Sr$

Show answer
Correct Option: B
Explanation:

Ans : $B$ $\rightarrow$ $Mg$

Generally melting point of the metals decreases down the group. But $Mg$ has anomalously low melting point in group $2$.
Group $2$ metals have metallic bonding. If we look at the crystal structure, $Be$ & $Mg$ are hexagonal close packed, $Ca$ & $Sr$ are face centered cubic.
At melting point, $Be$, $Ca$ and $Sr$ are body centered where as $Mg$ is hexagonal closed packed. Due to this arrangement, $Mg$ shows least melting point

In which case first has lower melting point than second?

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. Mg, Be

  2. Be, Ca

  3. Cs, Li

  4. K, Li

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Correct Option: A,C,D
Explanation:

(A) The melting point of magnesium is 924 K which is lower than the melting point of beryllium which is 1560 K.
(B) The melting point of beryllium is 1560 K which is higher than the melting point of calcium.
(C) The melting point of cesium is 302 K which is lower than the melting point of lithium which is 454 K.
(D) The melting point of potassium is 336 K which is lower than the melting point of Li which is 454 K.

In which case second has lower boiling point than first?

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. Li, K

  2. Be, Mg

  3. Li, Cs

  4. Ca, Mg

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Correct Option: A,B,C,D
Explanation:

(A) The boiling point of K is $1032$ K which is lower than that of Li ($1615$ K)
(B) The boiling point of Mg is $1363$ K which is lower than that of Be ( $2745$ K).
(C) The boiling point of Cs is $944$ K which is lower than that of Li ($1615$ K).
(D) The boiling point of Mg is $1363$ K is which is lower than that of Ca ($1767$ K).
Hence, all are correct.

The correct sequence of increasing melting point of $BeCl _{2},MgCl _{2},CaCl _{2},SrCl _{2}$ and $BaCl _{2}$ is

chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

  1. $BaCl _{2} < SrCl _{2} < CaCl _{2} < MgCl _{2} < BeCl _{2}$

  2. $BeCl _{2} < MgCl _{2} < CaCl _{2} < SrCl _{2} < BaCl _{2}$

  3. $BeCl _{2} < CaCl _{2} < MgCl _{2} < SrCl _{2} < BaCl _{2}$

  4. $MgCl _{2} < BeCl _{2} < SrCl _{2} < CaCl _{2} < BaCl _{2}$

Show answer
Correct Option: B