Alkynes - acidic character, preparation and addition — practice questions

Question 1 · difficulty L2 · understanding

Total number of sigma (σ) _______ and pi(π) ______ bonds respectively present in hex-1-en-4-yne are:

• A. 14 and 3
• B. 11 and 3
• C. 13 and 3
• D. 3 and 13

Question 2 · difficulty L2 · understanding

The incorrect statement regarding ethyne is

• A. The carbon - carbon bonds in ethyne is weaker than that in ethene
• B. Both carbons are sp hybridised
• C. The $$\mathrm{C}-\mathrm{C}$$ bonds in ethyne is shorter than that in ethene
• D. Ethyne is linear

Question 3 · difficulty L2 · understanding

Metallic sodium does not react normally with :

• A. gaseous ammonia
• B. But-2-yne
• C. Ethyne
• D. tert-butyl alcohol

Question 4 · difficulty L2 · understanding

Which of the following is Lindlar catalyst?

• A. Partially deactivated palladised charcoal
• B. Zinc chloride and HCl
• C. Sodium and Liquid NH 3
• D. Cold dilute solution of KMnO 4

Question 5 · difficulty L2 · understanding

Acetylene does not react with :

• A. $\mathrm{Na}$
• B. ammoniacal $\mathrm{AgNO}_3$
• C. $\mathrm{HCl}$
• D. $\mathrm{NaOH}$

Question 6 · difficulty L2 · understanding

The sum of sigma (σ) and pi (π) bonds in Hex-1,3-dien-5-yne is ________.

Question 7 · difficulty L2 · understanding

The number of sigma bonds in is _______________.

Question 8 · difficulty L3 · understanding

But-2-yne and hydrogen (one mole each) are separately treated with (i) $\mathrm{Pd} / \mathrm{C}$ and (ii) $\mathrm{Na} /$ liq. $\mathrm{NH}_3$ to give the products X and Y respectively. Identify the incorrect statements. A. X and Y are stereoisomers. B. Dipole moment of $X$ is zero. C. Boiling point of X is higher than Y . D. X and Y react with $\mathrm{O}_3 / \mathrm{Zn}+\mathrm{H}_2 \mathrm{O}$ to give different products. Choose the correct answer from the options given below :

• A. B and D Only
• B. A and C Only
• C. A and B Only
• D. B and C Only

Question 9 · difficulty L3 · understanding

Consider the following reaction : The product Y formed is :

• A. 2-methylhex-3-yne
• B. 5-methylhex-2-yne
• C. Isopropylbut-1-yne
• D. 2-methylhex-2-yne

Question 10 · difficulty L3 · understanding

80 mL of a hydrocarbon on mixing with 264 mL of oxygen in a closed U-tube undergoes complete combustion. The residual gases after cooling to 273 K occupy 224 mL . When the system is treated with KOH solution, the volume decreases to 64 mL . The formula of the hydrocarbon is :

• A. $\mathrm{C}_2 \mathrm{H}_2$
• B. $\mathrm{C}_2 \mathrm{H}_4$
• C. $\mathrm{C}_4 \mathrm{H}_{10}$
• D. $\mathrm{C}_2 \mathrm{H}_6$