Question

it takes 83.0mL of a 0.450 M naOH solution to neutralize 235 mL of an HCl solution. What is the concentration of the HCl solution.

Answer 1

0.159 M (3 s.f.)

Step-by-step explanation:

This is an acid- base reaction, which is also known as a neutralisation reaction.

`\boxed{acid \: + base→salt \: + water}`

1) Write out the balanced chemical equation.

NaOH (aq) +HCl (aq) → NaCl (aq) +H₂O(l)

The equation is balanced as on each side of the equation, there is 1 Na atom, 1 O atom, 2 H atoms and 1 Cl atom.

2) Find the number of moles of NaOH.

The symbol 'M' denotes Molarity, which is the number of moles per litre.

From the given concentration of NaOH,

1 L NaOH ----- 0.450 mol NaOH

Convert 83.0mL to litres:

Volume of NaOH

= 83 ÷1000

= 0.083 L

Moles of NaOH

= 0.083 ×0.450

= 0.03735 mol

3) Find the number of moles of HCl.

From the balanced equation, 1 mole of HCl is needed to neutralize 1 mole of NaOH.

Thus, amount of HCl

= 0.03735 mol

4) Calculate the concentration of HCl

Concentration= mol/ volume

Converting the volume from mL to L,

235 mL= 0.235 L

Concentration of HCl

= 0.03735 ÷0.235

= 0.15894 mol/L (5 s.f.)

= 0.159 M (3 s.f.)