Estimation of carbon, hydrogen, nitrogen, halogens, sulphur and phosphorus — NEET & JEE Questions

Question 1 · difficulty L1 · recall

In quantitative organic analysis, carbon and hydrogen are commonly estimated by complete combustion of the compound to form

• A. $CO_2$ and $H_2O$
• B. $CO$ and $H_2$
• C. $CH_4$ and $O_2$
• D. $C$ and $H_2$

Question 2 · difficulty L2 · understanding

In the Kjeldahl method, nitrogen present in a suitable organic compound is ultimately estimated from the amount of

• A. ammonia
• B. carbon dioxide
• C. chlorine
• D. sulfur dioxide

Question 3 · difficulty L2 · understanding

In Carius estimation of halogens, the halogen is commonly precipitated and weighed as

• A. silver halide
• B. sodium halide
• C. hydrogen halide gas
• D. elemental halogen only

Question 4 · difficulty L2 · understanding

In gravimetric estimation of sulfur after oxidation, sulfur is commonly weighed in the form of

• A. $BaSO_4$
• B. $SO_2$
• C. $H_2S$
• D. $Na_2S$

Question 5 · difficulty L3 · application

Combustion of an organic sample produces $4.40\,g$ of $CO_2$. What mass of carbon was present in the sample?

• A. 0.12 g
• B. 0.44 g
• C. 1.20 g
• D. 4.40 g

Question 6 · difficulty L3 · application

Combustion of an organic sample produces $1.80\,g$ of water. What mass of hydrogen was present in the sample?

• A. 0.10 g
• B. 0.20 g
• C. 0.90 g
• D. 1.80 g

Question 7 · difficulty L3 · application

A $0.50\,g$ organic sample gives $0.287\,g$ of AgCl in halogen estimation. What percentage of chlorine is present? Use molar masses AgCl = 143.5 and Cl = 35.5 g mol$^{-1}$.

• A. 7.1%
• B. 14.2%
• C. 28.4%
• D. 35.5%

Question 8 · difficulty L3 · application

A $0.40\,g$ organic compound gives $0.466\,g$ of $BaSO_4$ in sulfur estimation. What percentage of sulfur is present? Use molar masses $BaSO_4=233$ and S = 32 g mol$^{-1}$.

• A. 8%
• B. 16%
• C. 32%
• D. 40%

Question 9 · difficulty L4 · application

A $1.00\,g$ organic compound gives $2.20\,g$ of $CO_2$ and $0.90\,g$ of $H_2O$ on combustion. What are the percentages of carbon and hydrogen, respectively?

• A. 60% C and 10% H
• B. 50% C and 10% H
• C. 60% C and 20% H
• D. 27.3% C and 10% H

Question 10 · difficulty L4 · application

Which statement is a known limitation of the Kjeldahl method for nitrogen estimation?

• A. It is not generally suitable for nitrogen present in nitro or azo groups and some ring-nitrogen compounds
• B. It cannot be used for compounds containing carbon
• C. It measures chlorine instead of nitrogen
• D. It requires all nitrogen to be present as nitrate initially