Tag: alkali metals

Questions Related to alkali metals

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

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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. $Sr$

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

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Correct Option: B

Which element is most alkaline :

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

  1. F

  2. CI

  3. Br

  4. I

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Correct Option: A

Which of the alkaline earth elements forms covalent bonds ? 

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

  1. Ca

  2. Mg

  3. Sr

  4. Be

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Correct Option: D

Estimation of calcium and magnesium is done by :

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

  1. EDTA.

  2. oxalate.

  3. phosphate.

  4. None of these.

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Correct Option: A
Explanation:

Estimation of calcium and magnesium is done by EDTA in complexometric titration. Hexadentate ligand EDTA (ethylene diammine tetra acetate) forms metal chelates with calcium and magnesium. 

Lightest alkaline earth metal is :

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

  1. Be

  2. Mg

  3. Ca

  4. Sr

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Correct Option: A
Explanation:

Beryllium (Be), is the lightest alkaline earth metal with atomic number 4 and mass number 9.

Flame test is not given by :

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

  1. Ca

  2. Ba

  3. Be

  4. Li

Show answer
Correct Option: C
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.