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# How many grams of methylacetylene (propyne) CH3 - C Ξ CH will completely dischar...

### Question

How many grams of methylacetylene (propyne) CH3 - C Ξ CH will completely discharge the colour of 8g of bromine?

(Br = 80, C = 12, H = 1)

### Options

A)
0.5
B)
1.0 C)
2.0
D)
3.0
E)
4.0

### Explanation:

To answer this question, we need to know the balanced chemical equation for the reaction between methylacetylene (propyne) and bromine. The reaction is as follows:

CH3 - C ≡ CH + Br2 → CH3 - CBr = CHBr

Now, we need to find the number of moles of bromine (Br2) and use the stoichiometry of the reaction to find the mass of propyne needed to completely discharge the color of 8g of bromine.

First, let's find the molar mass of Br2:

Molar mass of Br2 = 2 * Br = 2 * 80 = 160 g/mol

Now, let's calculate the moles of Br2:

moles of Br2 = mass / molar mass = 8g / 160 g/mol = 0.05 mol

According to the balanced equation, 1 mole of propyne reacts with 1 mole of Br2. Therefore, we need 0.05 mol of propyne to react with 0.05 mol of Br2.

Now, let's find the molar mass of propyne (CH3 - C ≡ CH):

Molar mass of propyne = 3 * C + 4 * H = 3 * 12 + 4 * 1 = 36 + 4 = 40 g/mol

Finally, let's calculate the mass of propyne needed:

mass of propyne = moles * molar mass = 0.05 mol * 40 g/mol = 2 g

However, the question asks for the mass of methylacetylene (CH3 - C ≡ CH) needed to completely discharge the color of 8g of bromine. Since there's a triple bond in propyne, it will add two bromine atoms to the molecule, so we need to divide the mass of propyne by 2:

mass of propyne to completely discharge the color = 2 g / 2 = 1 g

So, 1.0 g of propyne is needed to completely discharge the color of 8g of bromine, which is Option B.