Post-UTME Chemistry 2019 Objective — Question 7

Question 7 of 20 from the Post-UTME Screening (Post-UTME) Chemistry 2019 Objective paper, with the correct answer and a full explanation.

How many grammes of methyl acetylene (propyne) CH3-C=CH will completely discharge the colour of 8g of bromine? [Br=80, C=12, H=1]

A. 0.5
B. 1.0
C. 2.0Correct
D. 3.0

Explanation

Molar mass of propyne (C3H4) = 40g/mol; Br2 = 160g/mol. Propyne + 2Br2 -> fully saturated addition product (decolourises 2 mol Br2 per mol alkyne). Moles Br2 = 8/160 = 0.05mol, needs 0.025mol propyne = 0.025 x 40 = 1.0g.

Sign up free to unlock

Score tracking
Practice history
Saved questions
Progress dashboard
Personalized sessions
Weak-topic breakdown

…and/or go further with premium services and No Ads.

Create free account

More questions from Chemistry 2019 Objective More Chemistry past papers