Question

Consider the balanced equation. 

PCl3 + 3H2O H3PO3 + 3HCl                 


What is the percent yield of HCl if 42.0 g of HCl are produced from the reaction of 62.0 g of PCl3?

A. 28.4%
B. 72.8%
C. 85.0%
D. 93.5%

PLZ HELP!!

Answer 1

Answer : The correct option is, (C) 85.0 %

Solution : Given,

Mass of
`PCl_3` = 62 g

Experimental yield of HCl = 42 g

Molar mass of
`PCl_3` = 137 g/mole

Molar mass of HCl = 36.5 g/mole

First we have to calculate the moles of
`PCl_3`.

`\text{Moles of }PCl_3=\frac{\text{Mass of }PCl_3}{\text{Molar mass of }PCl_3}=(62g)/(137g/mole)=0.452moles`

Now we have to calculate the moles of HCl.

The balanced chemical reaction is,

`PCl_3+3H_2O\rightarrow H_3PO_3+3HCl`

From the balanced reaction we conclude that

As, 1 moles of
`PCl_3` react to give 3 moles of
`HCl`

So, 0.452 moles of
`PCl_3` react to give
`3* 0.452=1.356` moles of
`HCl`

Now we have to calculate the mass of HCl.

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

`\text{Mass of }HCl=(1.356mole)* (36.5g/mole)=49.494g`

Therefore, the mass of HCl is, 49.494 g

Now we have to calculate the percent yield of HCl.

`\%\text{ yield of }HCl=\frac{\text{Actual yield of }HCl}{\text{Theoretical yield of }HCl}* 100=(42g)/(49.494g)* 100=84.85\%=85.0\%`

Therefore, the percent yield of HCl is, 85.0 %

Answer 2

Given:

PCl3 + 3H2O → H3PO3 + 3HCl

Mass of HCl = 42.9 g

Mass of PCl3 = 62.0 g

To determine:

% yield of HCl

Step-by-step explanation:

Molar mass of PCl3 = 137 g/mol

# moles of PCl3 reacted = mass/molar mass = 62 g/137 g.mol-1 = 0.453 moles

Based on the reaction stoichiometry:

1 mole of PCl3 produces 3 moles of HCl

therefore, 0.453 moles of PCl3 would be expected to produce: 0.453 * 3 = 1.359 moles of HCl

Molar mass of HCl = 36 g/mol

Therefore, expected mass (theoretical yield) of HCl = # moles of HCl * molar mass

= 1.359*36 = 48.92 g

% yield = (actual yield/theoretical yield)*100

% yield of HCl= (42.0/48.92)*100 = 85.9 %

Ans: (C)