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

Which of the following shows least melting point?

  1. $Be$
  2. $Mg$
  3. $Ca$
  4. $Sr$
Reveal answer Fill a bubble to check yourself
B Correct answer
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

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

In which case first has lower melting point than second?

  1. Mg, Be

  2. Be, Ca

  3. Cs, Li

  4. K, Li
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
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.

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

In which case second has lower boiling point than first?

  1. Li, K

  2. Be, Mg

  3. Li, Cs

  4. Ca, Mg
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
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.

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

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

  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. $MgCl _{2} < BeCl _{2} < SrCl _{2} < CaCl _{2} < BaCl _{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Melting points of alkaline earth metal halides generally increase as the lattice energy increases and the covalent character decreases. BeCl2 is highly covalent and has the lowest melting point, while BaCl2 is highly ionic with the highest melting point.

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

Flame test is not given by :

  1. Ca

  2. Ba

  3. Be

  4. Li
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Beryllium and magnesium do not give any colour to the flame test because they have a small size and very high ionization enthalpies. The energy of the flame is not sufficient to excite the electrons to higher energy levels. Hence, they do not impart any characteristic colour to the flame.

Hence option B is correct.

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

The first ionization energies of alkaline earth metals are higher than those of the alkali metals. This is because:

  1. there is increase in the nuclear charge of the alkaline earth metal

  2. there is decrease in the nuclear charge of the alkaline earth metal

  3. there is no change in the nuclear charge

  4. none ofthe above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As the nuclear charge increases it requires more energy to remove electron(Ionization energy) hence ionization energy will be increased. The first ionization energies of alkaline earth metals are higher than those of the alkali metals. This is because of the increase in the nuclear charge of the alkaline earth metal.