Question

I have 25mL of 1M HCl which neutralises 20mL of NaOH. What is the concentration of the NaOH?0.8 M1.0 M1.25 M

Answer 1

The concentration of the base is 1.25M

Step-by-step explanation

Given that;

The volume of HCl is 25mL

The concentration of HCl is 1M

The volume of NaOH is 20mL

Follow the steps below to find the concentration of NaOH

Step 1; Write a balanced equation for the reaction

`\text{ HCl}_((aq))\text{ }+\text{ NaOH}_((aq))\text{ }\rightarrow\text{ NaCl}_((aq))\text{ }+\text{ H}_2O_((l))`

In the reaction above, 1 mole HCl reacts with 1 mole NaOH to gives 1 mole NaCl and 1 mole H2O

Step 2; Find the concentration of NaOH using the below formula

`\text{ }\frac{\text{ CA VA}}{\text{ CB VB}}\text{ }=\frac{\text{ nA}}{\text{ nB}}`

Where

CA is the concentration of the acid

VA is the volume of the acid

CB is the concentration of the base

VB is the volume of the base

nA is the number of moles of the acid

nB is the number of mole of the base

Recall, that HCl is the acid and NaOH is the base

Step 3; Substitute the given data into the formula in step 2

`\begin{gathered} \text{ }\frac{\text{ 25 }*\text{ 1}}{20\text{ }*\text{ CB}}\text{ }=(1)/(1) \\ \\ \text{ }\frac{\text{ 25}}{\text{ 20CB}}\text{ }=(1)/(1) \\ \text{ cross multiply} \\ \text{ 25 }*\text{ 1 }=\text{ 1 }*\text{ 20CB} \\ \text{ 25 = 20CB} \\ \text{ Divide both sides by 20} \\ (25)/(20)\text{ = CB} \\ \text{ CB = 1.25M} \end{gathered}`

Therefore, the concentration of the base is 1.25M