Question

The colorless gas phosphorus trifluoride reacts slowly with water to give a mixture of phosphorus acid and hydrofluoric acid . (a) Write a balanced chemical equation for this reaction. + + (b) Determine the concentration (in moles per liter) of each of the acids that result from the complete reaction of 5.71×10-2 moles of phosphorus trifluoride with enough water to give a solution volume of 711 mL. phosphorus acid : M hydrofluoric acid : M

Answer 1

The balanced chemical reaction is given as:

`PF_3(g)+3H_2O(l)\rightarrow H_3PO_3(aq)+3HF(aq)`

b) Concentration of phosphorus acid is 0.0803 M.

Concentration of hydrofluoric acid is 0.241 M.

Step-by-step explanation:

a) The balanced chemical reaction is given as:

`PF_3(g)+3H_2O(l)\rightarrow H_3PO_3(aq)+3HF(aq)`

b)

Moles of phosphorus trifluoride gas =
`5.71* 10^(-2) mol`

`PF_3(g)+3H_2O(l)\rightarrow H_3PO_3(aq)+3HF(aq)`

According to reaction, 1 mole of phosphorus trifluoride gives 1 mole of phosphorus acid, then
`5.71* 10^(-2) mol` of phosphorus trifluoride will give:

`(1)/(1)* 5.71* 10^(-2) mol= 5.71* 10^(-2) mol` of phosphorus acid

Volume of the solution = V = 711 mL = 0.711 L ( 1 mL = 0.001 L)

`[concentration]=(Moles)/(Volume(L))`

Concentration of phosphorus acid :

`[H_3PO_3]=(5.71* 10^(-2) mol)/(0.711 L)=0.0803 M`

Concentration of phosphorus acid is 0.0803 M.

According to reaction, 1 mole of phosphorus trifluoride gives 3 mole of hydrofluoric acid, then
`5.71* 10^(-2) mol` of phosphorus trifluoride will give:

`(3)/(1)* 5.71* 10^(-2) mol= 0.1713 mol` of hydrofluoric acid

Volume of the solution = V = 711 mL = 0.711 L ( 1 mL = 0.001 L)

`[concentration]=(Moles)/(Volume(L))`

Concentration of hydrofluoric acid :

`[HF]=(0.1713 mol)/(0.711 L)=0.241 M`

Concentration of hydrofluoric acid is 0.241 M.