How to deal with the chemguys standard reference book Question series?

Main -Group chemistry
Subtopic: Group -1 ( alkali metals)
This is the part -1 Question series. It contains 8 MCQ questions.

Reference: Inorganic chemistry by Catherine E.Houscroft and Alane G.Sharpe (2nd edition)

Question 1:
Which of the following is a natural source of Na and B?

‌A) Carnalite
‌B) Chile Saltpetre
‌C) Borax
‌D) None of these

EXPLANATION:
Borax is a Na -containing mineral that is a commercially important source of B along with Na. So, the Correct Answer is C.



Question 2:
Which of the following metal is not Silvery-White? [1point]
‌A) Li
‌B) Na
‌C) K
‌D) Cs

Explanation:
The metals Li, Na, K, and Rb, are Silvery -White, but Cs has a golden-yellow Cast. So, the Correct answer is D .

Question 3:
Which of the following statements is correct?
‌A) For an alkali metal, the second ionization energy is very much higher than the first.
‌B) In the vapor state, Na2 molecules exist.
‌C) Down group 1, the ns-ns overlap becomes less effective.
‌D) All

EXPLANATION:
Alkali metals from Li to Cs have valence shell electronic configuration: ns1. So, removing the first electron is easy as it gets a noble gas electronic configuration, i.e., a stable electronic configuration.
But, the removal of the second electron is from a filled atomic orbital which demands high energy. That's why the second ionization energy of alkali metals is very much higher than the first .

In the vapor state, molecules of Na2 exist, and bonding is covalent, and B.O (Bond order)= 1.

In the periodic table, down the group of 1, the principal quantum number (n) of 's' orbital increases. Orbitals are more diffuse as n increases. So, down the group, 'as-is overlap becomes less effective, resulting in Weak M-M bonding.
So, the Correct answer is D.

Question 4:
The solid-state structure of the alkali metals is
‌A) face- centred cubic
‌B) body - centred cubic
‌C) simple Cubic
‌D) End- centred monoclinic
EXPLANATION:
The solid-state structure of the alkali metals is bcc(body-centered cubic).

    Fig: BCC (Body-centered cubic)

Question 5:  

At 298k  LiCl ,NaCl, KCl , RbCl have coordination number of ____.
‌A) 6
‌B)8
‌C) 12
‌D) 4
EXPLANATION:

At 298k, LiCl , NaCl , KCl , RbCl adopt an NaCl type structures having coordination number= 6.

Question 6:
Which of the following order of melting point is correct for group 1?
‌A)Li > Na > K> Rb > Cs
‌B) Li < Na < K ≈ Rb ≈ Cs
‌C) Cs > Rb > K> Na > Li
‌D) Rb > Cs > K > Na > Li.
Explanation:
As all the structures are the same type, a direct comparison of melting points is valid down the group. More diffuse orbitals as 'n' increases, so down the group, the ns-ns overlap becomes less effective, resulting in weak M-M bonding.
Thus, the order will be A.

Question 7:
Which of the following order is correct for ionic radius of group 1?
‌A) Rb+ > Cs+ > K+ > Na+ > Li+
‌B) Li+ > Na+ > K+ > Cs+ > Rb+
‌C) Na+ >Li+ > K+ > Cs+ >Rb+
‌D) Li+ >Na+>K+> Rb+>Cs+
EXPLANATION:
As charge constant, M+, so down the group 1, with adding one extra quantum shell, r+ increases. So, the Correct answer is A.

Question 8:
What is the order of bond dissociation energy of group 1?
‌A)Cs2 >Rb2 >K2>Na2 >Li2
‌B) Li2>Na2>K2>Cs2>Rb2
‌ C) Li2  > Na2  > K2 > Rb2 > Cs2
‌D) Li2>Na2>K2>Rb2=Cs2

EXPLANATION:
As with increasing principal quantum number, ns orbital diffuse and ns-ns overlap becomes less effective, resulting in weak M-M bonding and less bond dissociation energy.
Overlapping : 2s-2s >3s-3s>4s-4s>5s-5s
So , correct answer is C.