Question

Starting amount of NaOH = 70mLEnding amount of NaOH = 45 mLMolarity of NaOH = 1MSubtract these two numbers to get the amount NaOH used

Answer 1

The amount of mole of NaOH used is 0.025 mol

Step-by-step explanation

Given that;

The starting amount of NaOH is 70mL

The ending amount of NaOH is 45mL

The molarity of NaOH is 1M

Follow the steps below to find the amount of NaOH used

Step 1; Write the molarity formula

`\text{ Molarity = }\frac{\text{ moles of the solute}}{\text{ Volume of the solution}}`

Step 2; Convert the volume to liters

1mL is equivalent to 0.001L

`\begin{gathered} \text{ For V1 = 70mL} \\ \text{70 }*\text{ 0.001 =0.07L} \\ \text{ For V2 = 45mL} \\ \text{ 45 }*\text{ 0.001 = 0.045L} \end{gathered}`

The amount of NaOH used at the starting point can be calculated below as

`\begin{gathered} \text{ Molarity = }\frac{\text{ moles of the solute}}{\text{ volume}} \\ \text{ 1 = }\frac{\text{ moles}}{\text{ 0.07}} \\ \text{ cross multiply} \\ \text{ moles = 1 }*\text{ 0.07} \\ \text{ moles = 0.07 mol} \end{gathered}`

Therefore, the amount of NaOH used at the starting point is 0.07 mol

The amount of NaOH used at the ending point can be calculated below as

`\begin{gathered} \text{ molarity = }\frac{\text{ moles}}{\text{ volume}} \\ \text{ 1 = }\frac{\text{ moles}}{\text{ 0.045}} \\ \text{ cross multiply} \\ \text{ moles = 1 }*\text{ 0.045} \\ \text{ moles = 0.045 mol} \end{gathered}`

Step 3; Calculate the amount of NaOH used

`\begin{gathered} \text{ The amount of NaOH used = 0.07 - 0.045} \\ \text{ The amount of NaOH used = 0.025 mol} \end{gathered}`

Therefore, the amount of mole of NaOH used is 0.025 mol