How many grams of bromine will be required to completely react with 10 g of propyne?
(C = 12, H = 1, Br = 80)
- 20 g
- 40 g
- 60 g
-
80 g
The correct answer is: D
Explanation
Firstly, you must get the correct chemical equation for the reaction, if not, you will get the answer wrong.
Possible equations are:
Br\(_2\) + C\(_3\)H\(_4\) → C\(_3\)H\(_4\)Br\(_2\) - This equation is wrong, so don't fall for this.
2Br\(_2\) + C\(_3\)H\(_4\) → CH\(_3\)CBr\(_2\)CHBr\(_2\) - This is the correct equation because the reaction is an electrophylic addition reaction, where the bromine molecules add to the triple bond in propyne.When propyne reacts with bromine, the primary product formed is 1,1,2,2-tetrabromopropane; this reaction causes the reddish-brown colour of bromine to disappear as the bromine is added across the triple bond of propyne, resulting in a colorless product.
2Br\(_2\) + C\(_3\)H\(_4\) → CH\(_3\)CBr\(_2\)CHBr\(_2\)
(4 X 80)g (36 + 4)g
320 g of C\(_3\)H\(_4\) reacts with 40 g of Br
X g will react with 10g of C\(_3\)H\(_4\)
(10)/(40) x (320) /(1) = 80g
If you apply the first equation, you would obtain option B (40g) which is wrong. However, the reaction of Bromine with propyne would yield 1,1,2,2- tetrabromopropane not 1,2- dibromopropene.