What is the structure of $\mathrm{BeCl}_2$ molecule in gaseous and solid state?
Beryllium chloride has different structures in solid and vapour state. In solid state, it exists in the form of polymeric chain structure in which each Be-atom is surrounded by four chlorine atoms having two of the chlorine atoms covalently bonded while the other two by coordinate bonds. The resulting bridge structure contains infinite chains.
In vapour state, above 1200 K , it exists as a monomer having linear structure and zero dipole moment. But below 1200 K , it exists as dimer structure even in vapour state.
Match the elements given in Column I with the properties mentioned in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Li | 1. | Insoluble sulphate |
| B. | Na | 2. | Strongest monoacidic base |
| C. | Ca | 3. | Most negative $E^{\ominus}$ value among alkali metals |
| D. | Ba | 4. | Insoluble oxalate |
| 5. | 6s$$^2$$ outer electronic configuration |
A. $\rightarrow(3)$
B. $\rightarrow(2)$
C. $\rightarrow(4)$
D. $\rightarrow(5)$
A. Li-Most negative $E^{-}$among alkali metals
[Due to very high hydration energy the resulting $E^{\ominus}$ is most negative].
B. Na-Strongest monoacidic base
[Alkalies are more acidic than alkaline earth metals. LiOH has covalent character].
C. Ca-insoluble oxalate
[Calciuim oxalate is insoluble in water]
D. Ba-Insoluble sulphate
[Hydration energy decreases as size of cation increases].
$6 s^2$ outer electronic configuration
$$\left.{ }_{56} \mathrm{Ba}=1 s^2, 2 s^2, 2 p^6, 3 s^2, 3 p^6, 3 d^{10}, 4 s^2, 4 p^6, 4 d^{10}, 5 s^2, 5 p^6, 6 s^2\right]$$
Match the compounds given in Column I with their uses mentioned in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | CaCO$$_3$$ | 1. | Dentistry, ornamental work |
| B. | Ca(OH)$$_2$$ | 2. | Manufacture of sodium carbonate from caustic soda |
| C. | CaO | 3. | Manufacture of high quality paper |
| D. | CaSO$$_4$$ | 4. | Used in white washing |
A. $\rightarrow$ (3)
B. $\rightarrow$ (4)
C. $\rightarrow(2)$
D. $\rightarrow 1$
A. $\mathrm{CaCO}_3-$ Manufacture of high quality paper
B. $\mathrm{Ca}(\mathrm{OH})_2-$ Used in white washing
C. $\mathrm{CaO}-$ Manufacture of sodium carbonate from caustic soda
D. $\mathrm{CaSO}_4-$ Dentistry, ornamental work
Match the elements given in Column I with the colour they impart to the flame given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Cs | 1. | Apple green |
| B. | Na | 2. | Violet |
| C. | K | 3. | Brick reduction |
| D. | Ca | 4. | Yellow |
| E. | Sr | 5. | Crimson red |
| F. | Ba | 6. | Blue |
A. $\rightarrow$ (6)
B. $\rightarrow$ (4)
C. $\rightarrow(2)$
D. $\rightarrow$ (3)
E. $\rightarrow$ (5)
F. $\rightarrow 1$
Elements with the characteristic flame colour are as follows
A. Cs - Blue
B. $\mathrm{Na}-$ Yellow
C. K - Violet
D. Ca - Brick red
E. Sr - Crimson red
F. Ba - Apple green
Flame colours are produced from the movement of the electrons in the metal ions present in the compounds. These movement of electrons (electronic excitation-de-excitation) requires energy.
Each atom has particular energy gap between ground and excited energy level therefore each of these movements involves a specific amount of energy emitted as light energy, and each corresponds to a particular colour. As we know energy gap between ground and excited state energy level increases wavelength of decreases and complemently colouer is observed as a result.
Assertion (A) The carbonate of lithium decomposes easily on heating to form lithium oxide and $\mathrm{CO}_2$.
Reason (R) Lithium being very small in size polarises large carbonate ion leading to the formation of more stable $\mathrm{Li}_2 \mathrm{O}$ and $\mathrm{CO}_2$.