Question

Phosphorous reacts with chlorine gas to produce phosphorous pentachloride. Calculate the mass of product produced when 25.0 g of phosphorous reacts with 25.0 grams of chlorine. Calculate the mass of product produced if the reaction occurred with a 70.5 percent yield.

Answer 1

Answer : The mass of product produced if the reaction occurred with a 70.5 percent yield will be, 20.67 grams.

Explanation : Given,

Mass of P = 25 g

Mass of
`Cl_2` = 25 g

Molar mass of P = 30.97 g/mole

Molar mass of
`Cl_2` = 71 g/mole

Molar mass of
`PCl_5` = 208.24 g/mole

First we have to calculate the moles of
`P` and
`Cl_2`.

`\text{Moles of }P=\frac{\text{Mass of }P}{\text{Molar mass of }P}=(25g)/(30.97g/mole)=0.807moles`

`\text{Moles of }Cl_2=\frac{\text{Mass of }Cl_2}{\text{Molar mass of }Cl_2}=(25g)/(71g/mole)=0.352moles`

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

`2P+5Cl_2\rightarrow 2PCl_5`

From the balanced reaction we conclude that

As, 5 moles of
`Cl_2` react with 2 moles of
`P`

So, 0.352 moles of
`Cl_2` react with
`(2)/(5)* 0.352=0.1408` moles of
`P`

That means, in the given balanced reaction,
`Cl_2` is a limiting reagent and it limits the formation of products and
`P` is an excess reagent because the given moles are more than the required moles.

Now we have to calculate the moles of
`PCl_5`.

As, 5 moles of
`Cl_2` react with 2 moles of
`PCl_5`

So, 0.352 moles of
`Cl_2` react with
`(2)/(5)* 0.352=0.1408` moles of
`PCl_5`

Now we have to calculate the mass of
`PCl_5`.

`\text{Mass of }PCl_5=\text{Moles of }PCl_5* \text{Molar mass of }PCl_5`

`\text{Mass of }PCl_5=(0.1408mole)* (208.24g/mole)=29.32g`

Now we have to calculate the mass of product produced (actual yield).

`\%\text{ yield of }PCl_5=\frac{\text{Actual yield of }PCl_5}{\text{Theoretical yield of }PCl_5}* 100`

`70.5=\frac{\text{Actual yield of }PCl_5}{29.32g}* 100`

`\text{Actual yield of }PCl_5=20.67g`

Therefore, the mass of product produced if the reaction occurred with a 70.5 percent yield will be, 20.67 grams.