Group 13 - boron, borax, boric acid, diborane and aluminium — practice questions

Question 1 · difficulty L2 · understanding

If the formula of Borax is $$\mathrm{Na_2B_4O_x(OH)_y~.~zH_2O}$$, then $$x+y+z=$$ ___________

Question 2 · difficulty L2 · understanding

Three moles of B 2 H 6 are completely reacted with methanol. The number of moles of boron containing product formed is ____________.

Question 3 · difficulty L2 · understanding

The value of $$n$$ in the molecular formula $$\mathrm{Be_n Al_2Si_6O_{18}}$$ is ___________.

Question 4 · difficulty L2 · understanding

Given below are two statements : Statement I : Aluminium is more electropositive than thallium as the standard electrode potential value of $\mathrm{E}^{\circ} \mathrm{Al}^{3+} / \mathrm{Al}$ is negative and $\mathrm{E}^{\circ} \mathrm{Tl}^{3+} / \mathrm{Tl}$ is positive. Statement II : The sum of first three ionization enthalpies of boron is very high when compared to that of aluminium. Due to this reason boron forms covalent compounds only and aluminium forms $\mathrm{Al}^{3+}$ ion. In the light of the above statements, choose the correct answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Question 5 · difficulty L2 · understanding

Given below are two statements : Statement I : Gallium is used in the manufacturing of thermometers. Statement II : A thermometer containing gallium is useful for measuring the freezing point $$(256 \mathrm{~K})$$ of brine solution. In the light of the above statements, choose the correct answer from the options given below :

• A. Both Statement I and Statement II are true
• B. Statement I is true but Statement II is false
• C. Statement I is false but Statement II is true
• D. Both Statement I and Statement II are false

Question 6 · difficulty L2 · understanding

The number of neutrons present in the more abundant isotope of boron is '$$x$$'. Amorphous boron upon heating with air forms a product, in which the oxidation state of boron is '$$y$$'. The value of $$x+y$$ is _________ .

• A. 9
• B. 6
• C. 4
• D. 3

Question 7 · difficulty L2 · understanding

For a good quality cement, the ratio of silica to alumina is found to be :

• A. 1.5
• B. 2
• C. 3
• D. 4.5

Question 8 · difficulty L2 · understanding

The covalency and oxidation state respectively of boron in $$\left[\mathrm{BF}_{4}\right]^{-}$$, are :

• A. 3 and 4
• B. 4 and 3
• C. 4 and 4
• D. 3 and 5

Question 9 · difficulty L2 · understanding

The incorrect statement from the following for borazine is :

• A. It can react with water.
• B. It is a cyclic compound.
• C. It has electronic delocalization.
• D. It contains banana bonds.

Question 10 · difficulty L2 · understanding

Given below are two statements : Statement I : Boron is extremely hard indicating its high lattice energy. Statement II : Boron has highest melting and boiling point compared to its other group members. In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both Statement I and Statement II are incorrect
• B. Statement I is incorrect but Statement II is correct
• C. Statement I is correct but Statement II is incorrect
• D. Both statement I and Statement II are correct