The element which exists in liquid state for a wide range of temperature and can be used for measuring high temperature is
Which of the following is a Lewis acid?
The geometry of a complex species can be understood from the knowledge of type of hybridisation of orbitals of central atom. The hybridisation of orbitals of central atom in $\left[\mathrm{B}\left(\mathrm{OH}_4\right)\right]^{-}$and the geometry of the complex are respectively
Which of the following oxides is acidic in nature?
The exhibition of highest coordination number depends on the availability of vacant orbitals in the central atom. Which of the following elements is not likely to act as central atom in $M \mathrm{~F}_6^{3-}$ ?
Boric acid is an acid because its molecule
Catenation i.e., linking of similar atoms depends on size and electronic configuration of atoms. The tendency of catenation in group 14 elements follows the order
Silicon has a strong tendency to form polymers like silicones. The chain length of silicone polymer can be controlled by adding
Ionisation enthalpy $\left(\Delta_i \mathrm{H} \mathrm{kJ} \mathrm{mol}^{-1}\right)$ for the elements of group 13 follows the order
In the structure of diborane,
A compound X , of boron reacts with $\mathrm{NH}_3$ on heating to give another compound $Y$ which is called inorganic benzene. The compound $X$ can be prepared by treating $\mathrm{BF}_3$ with lithium aluminium hydride. The compounds $X$ and $Y$ are represented by the formulas.
Quartz is extensively used as a piezoelectric material, it contains .......... .
The most commonly used reducing agent is
Dry ice is
Cement, the important building material is a mixture of oxides of several elements. Besides calcium, iron and sulphur, oxides of elements of which of the group $(s)$ are present in the mixture?
Assertion (A) If aluminium atoms replace a few silicon atoms in three dimensional network of silicon dioxide, the overall structure acquires a negative charge.
Reason (R) Aluminium is trivalent while silicon is tetravalent.
Assertion (A) Silicones are water repelling in nature.
Reason (R) Silicones are organosilicon polymers, which have $\left(-R_2 \mathrm{SiO}-\right)$ as repeating unit.
The reason for small radius of Ga compared to Al is ............ .
The linear shape of $\mathrm{CO}_2$ is due to ............ .
$\mathrm{M}_3 \mathrm{SiO}$ is used during polymerisation of organo silicones because
Which of the following statements are correct ?
Which of the following statements are correct? Answer on the basis of given figure.
Identify the correct resonance structures of carbon dioxide from the ones given below
Draw the structures of $\mathrm{BC}_3 \cdot \mathrm{NH}_3$ and $\mathrm{Ald}_3$ (dimer).
Explain the nature of boric acid as a Lewis acid in water.
Draw the structure of boric acid showing hydrogen bonding. Which species is present in water ? What is the hybridisation of boron in this species ?
Explain why the following compounds behave as Lewis acids ?
(a) $\mathrm{Bd}_3$
(b) $\mathrm{Ald}_3$
Give reasons for the following
(a) $\mathrm{CCl}_4$ is immiscible in water, whereas $\mathrm{Sid}_4$ is easily hydrolysed.
(b) Carbon has a strong tendency for catenation compared to silicon.
Explain the following.
(a) $\mathrm{CO}_2$ is a gas whereas $\mathrm{SiO}_2$ is a solid.
(b) Silicon forms $\mathrm{SiF}_6^{2-}$ ion whereas corresponding fluoro compound of carbon is not known.
The +1 oxidation state in group 13 and +2 oxidation state in group 14 becomes more and more stable with increasing atomic number. Explain.
Carbon and silicon both belong to the group 14, but inspite of the stoichiometric similarity, the dioxides, (i.e., carbon dioxide and silicon dioxide), differ in their structures . Comment.
If a trivalent atom replaces a few silicon atoms in three dimensional network of silicon dioxide, what would be the type of charge on overall structure?
When $\mathrm{BC}_3$ is treated with water, it hydrolyses and forms $\left[\mathrm{B}[\mathrm{OH}]_4\right]^{-}$ only whereas $\mathrm{Ald}_3$ in acidified aqueous solution forms $\left[\mathrm{Al}\left[\mathrm{H}_2 \mathrm{O}\right]_6\right]^{3+}$ ion. Explain what is the hybridisation of boron and aluminium in these species?
Aluminium dissolves in mineral acids and aqueous alkalies and thus shows amphoteric character. A piece of aluminium foil is treated with dilute hydrochloric acid or dilute sodium hydroxide solution in a test tube and on bringing a burning matchstick near the mouth of the test tube, a pop sound indicates the evolution of hydrogen gas. The same activity when performed with concentrated nitric acid, reaction doesn't proceed. Explain the reason.
Explain the following.
(a) Gallium has higher ionisation enthalpy than aluminium.
(b) Boron does not exist as $\mathrm{B}^{3+}$ ion.
(c) Aluminium forms $\left[\mathrm{AlF}_6\right]^{3-}$ ion but boron does not form $\left[\mathrm{BF}_6\right]^{3-}$ ion.
(d) $\mathrm{Pb} X_2$ is more stable than $\mathrm{PbX}_4$.
(e) $\mathrm{Pb}^{4+}$ acts as an oxidising agent but $\mathrm{Sn}^{2+}$ acts as a reducing agent.
(f) Electron gain enthalpy of chlorine is more negative as compared to fluorine.
(g) $\mathrm{Tl}\left(\mathrm{NO}_3\right)_3$ acts as an oxidising agent.
(h) Carbon shows catenation property but lead does not.
(i) $\mathrm{BF}_3$ does not hydrolyse.
(j) Why does the element silicon, not form a graphite like structure whereas carbon does
Identify the compounds $A, X$ and $Z$ in the following reactions.
$$A+2 \mathrm{HC}+5 \mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{NaC}+X$$
$X \xrightarrow[370 \mathrm{~K}]{\Delta} \mathrm{HBO}_2 \underset{>370 \mathrm{~K}}{\stackrel{\Delta}{\longrightarrow}} Z$
Complete the following chemical equations.
$$\begin{gathered} \mathrm{Z}+3 \mathrm{LiAlH}_4 \longrightarrow X+3 \mathrm{LiF}+3 \mathrm{AlF}_3 \\ X+6 \mathrm{H}_2 \mathrm{O} \longrightarrow Y+6 \mathrm{H}_2 \\ 3 X+3 \mathrm{O}_2 \xrightarrow{\Delta} \mathrm{B}_2 \mathrm{O}_3+3 \mathrm{H}_2 \mathrm{O} \end{gathered}$$
Match the species given in Column I with the properties mentioned in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | BF$$_4^-$$ | 1. | Oxidation state of central atom is +4 |
| B. | AlCl$$_3$$ | 2. | Strong oxidising agent |
| C. | SnO | 3. | Lewis acid |
| D. | PbO$$_2$$ | 4. | Can be further oxidised |
Match the species given in Column I with properties given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Diborane | 1. | Used as a flux for soldering metals |
| B. | Gallium | 2. | Crystalline form of silica |
| C. | Borax | 3. | Banana bonds |
| D. | Aluminosilicate | 4. | Low melting, high boiling, useful for measuring high temperatures |
| E. | Quartz | 5. | Used as catalyst in petrochemical industries |
Match the species given in Column I with the hybridisation given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Boron in [B(OH$$_4$$)]$$^-$$ | 1. | sp$$^2$$ |
| B. | Aluminium in $\left[\mathrm{Al}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}$ | 2. | sp$$^3$$ |
| C. | Boron in B$$_2$$H$$_6$$ | 3. | sp$$^3$$d$$^2$$ |
| D. | Carbon in buckminster fullerene | ||
| E. | Silicon in SiO$$_4^{-4}$$ | ||
| F. | Germanium in $\left[\mathrm{GeCl}_6\right]^{2-}$ |
Describe the general trends in the following properties of the elements in groups 13 and 14.
(a) Atomic size
(b) Ionisation enthalpy
(c) Metallic character
(d) 0xidation states
(e) Nature of halides
Account for the following observations.
(a) $\mathrm{AlCl}_3$ is a Lewis acid.
(b) Though fluorine is more electronegative than chlorine yet $\mathrm{BF}_3$ is a weaker Lewis acid than $\mathrm{CI}_3$.
(c) $\mathrm{PbO}_2$ is a stronger oxidising agent than $\mathrm{SnO}_2$.
(d) The +1 oxidation state of thallium is more stable than its +3 state.
When aqueous solution of borax is acidified with hydrochloric acid, a white crystalline solid is formed which is soapy to touch. Is this solid acidic or basic in nature ? Explain.
Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Given reason for your choice. State the nature of bonding also.
(a) $\mathrm{TlCl}_3, \mathrm{TlCl}$
(b) $\mathrm{AlCl}_3, \mathrm{AlCl}$
(c) $\mathrm{InCl}_3, \mathrm{InCl}$
$\mathrm{BCl}_3$ exists as monomer whereas $\mathrm{AlCl}_3$ is dimerised through halogen bridging. Give reason. Explain the structure of the dimer of $\mathrm{AlCl}_3$ also.
Boron fluoride exists as $\mathrm{BF}_3$ but boron hydride doesn't exist as $\mathrm{BH}_3$. Give reason. In which form does it exist ? Explain its structure.
(a) What are silicones? State the uses of silicones.
(b) What are boranes ? Give chemical equation for the preparation of diborane.
A compound (A) of boron reacts with $\mathrm{NMe}_3$ to give an adduct (B) which on hydrolysis gives a compound (C) and hydrogen gas. Compound (C) is an acid. Identify the compounds A, B, and C. Give the reactions involved.
A non-metallic element of group 13, used in making bullet proof vests is extremely hard solid of black colour. It can exist in many allotropic forms and has unusually high melting point. Its trifluoride acts as Lewis acid towards ammonia.
The element exihibits maximum covalency of four. Identify the element and write the reaction of its trifluoride with ammonia. Explain why does the trifluoride act as a Lewis acid?
A tetravalent element forms monoxide and dioxide with oxygen. When air is passed over heated element ( 1273 K ), producer gas is obtained. Monoxide of the element is a powerful reducing agent and reduces ferric oxide to iron.
Identify the element and write formulae of its monoxide and dioxide. Write chemical equations for the formation of producer gas and reduction of ferric oxide with the monoxide.