NEET Organic Chemistry Some Basic Principles and Techniques — Set 7

Question 1

In Lassaigne’s test, the formation of a blood-red color indicates the presence of which two elements together?

Accepted Answer

When both nitrogen and sulphur are present, they form $ \ce{NaSCN} $, which reacts with $ \ce{Fe^{3+}} $ to give a blood-red color ($ \ce{Fe(SCN)3} $).

Question 2

In the estimation of carbon and hydrogen, 0.3 g of a compound gave 0.88 g of $ \ce{CO2} $. What is the percentage of carbon?

Accepted Answer

Mass of C = $ \frac{12}{44} \times 0.88 = 0.24 $ g. Percentage = $ \frac{0.24}{0.3} \times 100 = 80\% $.

Question 3

Which reagent is used in Lassaigne’s test to detect sulphur?

Accepted Answer

Sodium nitroprusside reacts with $ \ce{Na2S} $ (formed from sulphur) to produce a violet color in Lassaigne’s test.

NEET Chemistry: Organic Chemistry Some Basic Principles and Techniques — Practice Set 7

Q1. In Lassaigne’s test, the formation of a blood-red color indicates the presence of which two elements together?

Q2. In the estimation of carbon and hydrogen, 0.3 g of a compound gave 0.88 g of \( \ce{CO2} \). What is the percentage of carbon?

Q3. Which reagent is used in Lassaigne’s test to detect sulphur?

Q4. The most electronegative carbon atom is found in which type of hybridization?

Q5. What is the hybridization of the carbon atom attached to the oxygen in \( \ce{CH3CH2OH} \)?

Q6. What is the shape around the carbon atom in \( \ce{CH3C#CH} \) that is triple-bonded?

Q7. Which of the following has the lowest boiling point?

Q8. Which carbon in \( \ce{CH3CH2CH2CH=CH2} \) is most affected by the inductive effect of the double bond?

Q9. In the estimation of carbon and hydrogen, 0.18 g of a compound gave 0.528 g of \( \ce{CO2} \) and 0.108 g of \( \ce{H2O} \). What is the empirical formula?

Q10. In the estimation of carbon, 0.12 g of a compound gave 0.44 g of \( \ce{CO2} \). What is the percentage of carbon?