1
Question
1) Write molecularity of the following reaction:
2NO(g)+O2(g)→2NO2(g)
2) What is 'calcination'? How does it differ from 'roasting'?
3) Write resonating structures of ozones,
4) The decomposition of N2O5(g) at 320 K according to the following equation follows first order reaction:
N2O5(g)→2NO2(g)+12O2(g)
The initial concentration of N2O5(g) is 1.24×10−2mol.L−1 and after 60 minutes, 0.20×10−2mol.L−1. Calculate the rate constant of the reaction at 320 K
2NO(g)+O2(g)→2NO2(g)
2) What is 'calcination'? How does it differ from 'roasting'?
3) Write resonating structures of ozones,
4) The decomposition of N2O5(g) at 320 K according to the following equation follows first order reaction:
N2O5(g)→2NO2(g)+12O2(g)
The initial concentration of N2O5(g) is 1.24×10−2mol.L−1 and after 60 minutes, 0.20×10−2mol.L−1. Calculate the rate constant of the reaction at 320 K
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Solution
1) Molecularity is the sum of the different reactants which take part in a chemical reaction. Thus, molecularity of the reaction
2NO(g)+O2(g)→2NO2(g) is (2+1)=3
2) Calcination : Calcination is a process in which the ore of a metal or other solid material is heated to a high temperature below the melting point of the metal in absence of air or limited supply of air.
Example: Decomposition of carbonate minerals as in the calcination of limestone to drive off CO2
CacO3(s)→CaO(s)+CO2(g)
3) Difference between Calcination and Roasting
Calcination Roasting (i) Ore is heated in the absence or limited supply of oxygen or air Ore is heated in the presence or excess of oxygen or air. (ii) This method is employed for carbonate ores. This method is employed for sulphide ores. (iii) Carbon dioxide is produced along with metal oxide. Sulphur dioxide is produced along with metal oxide. (iv) Examples:
ZnCO3Δ−→ZnO+CO2
CuCO3(→Δ)CuO+CO2 Examples:
2ZnS+3O2Δ−→2ZnO+2SO2
2Cu2S+3O2Δ−→2Cu2O+2SO2
4) The resonating structures of ozone are given below:
O3 exist as a hybrid of structure I and structure II
Each atom may be thought as roughly sp2 hybrid. The middle O atom has a lone pair of electrons with a delocalised π orbital over all the three oxygen atoms.
The rate constant (K) of first order reaction at temp t is given by
K=2.303tlogCoCt
where, Co= initial concentration, Ct= concentration after time t
For N2O5(g)→2NO2(g)+12O2(g)
Co=1.24×10−2mol L−1,Ct=0.20×10−2mol L−1,t=60 min
K=2.30360×log1.24×10−2mol L−10.20×10−2mol L−1
=0.038×log(6.2)min−1
=0.038×0.792 min−1=0.030 min−1
Thus, rate constant of the reaction at 320K is 0.030 min−1
2NO(g)+O2(g)→2NO2(g) is (2+1)=3
2) Calcination : Calcination is a process in which the ore of a metal or other solid material is heated to a high temperature below the melting point of the metal in absence of air or limited supply of air.
Example: Decomposition of carbonate minerals as in the calcination of limestone to drive off CO2
CacO3(s)→CaO(s)+CO2(g)
Example: Decomposition of carbonate minerals as in the calcination of limestone to drive off CO2
CacO3(s)→CaO(s)+CO2(g)
3) Difference between Calcination and Roasting
| Calcination | Roasting |
| (i) Ore is heated in the absence or limited supply of oxygen or air | Ore is heated in the presence or excess of oxygen or air. |
| (ii) This method is employed for carbonate ores. | This method is employed for sulphide ores. |
| (iii) Carbon dioxide is produced along with metal oxide. | Sulphur dioxide is produced along with metal oxide. |
| (iv) Examples: ZnCO3Δ−→ZnO+CO2 CuCO3(→Δ)CuO+CO2 | Examples: 2ZnS+3O2Δ−→2ZnO+2SO2 2Cu2S+3O2Δ−→2Cu2O+2SO2 |
4) The resonating structures of ozone are given below:
O3 exist as a hybrid of structure I and structure II
Each atom may be thought as roughly sp2 hybrid. The middle O atom has a lone pair of electrons with a delocalised π orbital over all the three oxygen atoms.
The rate constant (K) of first order reaction at temp t is given by
K=2.303tlogCoCt
where, Co= initial concentration, Ct= concentration after time t
For N2O5(g)→2NO2(g)+12O2(g)
Co=1.24×10−2mol L−1,Ct=0.20×10−2mol L−1,t=60 min
K=2.30360×log1.24×10−2mol L−10.20×10−2mol L−1
=0.038×log(6.2)min−1
=0.038×0.792 min−1=0.030 min−1
Thus, rate constant of the reaction at 320K is 0.030 min−1
O3 exist as a hybrid of structure I and structure II
Each atom may be thought as roughly sp2 hybrid. The middle O atom has a lone pair of electrons with a delocalised π orbital over all the three oxygen atoms.
The rate constant (K) of first order reaction at temp t is given by
K=2.303tlogCoCt
where, Co= initial concentration, Ct= concentration after time t
For N2O5(g)→2NO2(g)+12O2(g)
Co=1.24×10−2mol L−1,Ct=0.20×10−2mol L−1,t=60 min
K=2.30360×log1.24×10−2mol L−10.20×10−2mol L−1
=0.038×log(6.2)min−1
=0.038×0.792 min−1=0.030 min−1
Thus, rate constant of the reaction at 320K is 0.030 min−1
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