Answer : The final hydrogen ion concentration is
![1.58* 10^(-13)M](https://img.qammunity.org/2021/formulas/chemistry/college/jvaxszqnoayc5ir5dmniqp10rzcwltvv6i.png)
Explanation :
The chemical reaction equation will be:
![H_3PO_4+3NaOH\rightarrow Na_3PO_4+3H_2O](https://img.qammunity.org/2021/formulas/chemistry/college/tk6cc6j5edl0mwiwm4syd7cypmaoukmsr0.png)
In this reaction, 1 mole of
reacts with 3 mole NaOH.
So, the number of moles of
present in 150 ml of 0.1 M solution is calculated as follows.
Number of moles = Concentration × Volume
Number of moles = 0.1 M ×0.150 L = 0.015 mol
As it reacts with 3 moles of NaOH.
Number of moles of NaOH = 3 × 0.015 mol = 0.045 mol
So, moles of NaOH in 400 mL of 0.2 M NaOH is as follows.
Number of moles = 0.2 M × 0.4 L = 0.080 mol
Number of moles remained after the reaction = (0.080 - 0.045) mol = 0.035 mol NaOH in 550 ml (400 ml + 150 ml)
As molarity is the number of moles present in liter of solution. Hence, molarity of NaOH is as follows.
![\text{Molarity}=\frac{\text{Number of moles}}{\text{Volume of solution}}](https://img.qammunity.org/2021/formulas/chemistry/college/gnvb5wuaynfdhpsoofiqfih2s7tj09l5pk.png)
![\text{Molarity}=(0.035mol)/(0.550L)=0.0636M](https://img.qammunity.org/2021/formulas/chemistry/college/imguwu1tglzp44q3w27aygamfr4px61509.png)
Now we have to determine the hydroxide ion concentration.
As,
= 0.0636 M
![pOH=-\log [OH^-]](https://img.qammunity.org/2021/formulas/chemistry/college/hdm1ob4dj6mx2sy3kobrrj91lzbh3927bk.png)
![pOH=-\log 0.0636](https://img.qammunity.org/2021/formulas/chemistry/college/q7nwe3bl2kmqglwf4mff4qmp60cjtxynl2.png)
![pOH=1.20](https://img.qammunity.org/2021/formulas/chemistry/college/1fgi2mdv2h9yqg9lzh62l8q2mwo8kn8gv9.png)
Now we have to determine the pH.
As, pH + pOH = 14
pH = 14 - pOH
pH = 14 - 1.20
pH = 12.8
Now we have to determine the hydrogen ion concentration.
![pH=-\log [H^+]](https://img.qammunity.org/2021/formulas/chemistry/high-school/rjo2yhb5oj9ry1fr4db1ujrazm6fh3vhke.png)
![12.8=-\log [H^+]](https://img.qammunity.org/2021/formulas/chemistry/college/nxx5nqx7yro4tbye1icxyzmm1kygh6o2o3.png)
![[H^+]=1.58* 10^(-13)M](https://img.qammunity.org/2021/formulas/chemistry/college/o4b2ivexhkacpkunazcsr7y7m77gt2r71a.png)
Therefore, the final hydrogen ion concentration is
![1.58* 10^(-13)M](https://img.qammunity.org/2021/formulas/chemistry/college/jvaxszqnoayc5ir5dmniqp10rzcwltvv6i.png)