Question

Similar to lab! H3C6H507 (citric acid) reacts with sodium hydroxide in the following chemical reaction:H3C6H5O7 (aq) + 3 NaOH (aq) --> Na3C6H5O7 (aq) + 3 H₂O (1)The titration of 20.0 mL of H3C6H507 solution of unknown concentration requires 18.4 mL of 0.100 M NaOH to reach the equivalencepoint.What is the concentration of H3C6H507 in Molarity (moles of H3C6H507 per L of solution)?For the toolbar press ALT+F10 (PC) or ALT+EN+F10 (Mac)

Answer 1

1) Balance the chemical equation.

`H_3C_6H_5O_(7(aq))+3NaOH_((aq))\rightarrow Na_3C_6H_5O_(7(aq))+3H_2O_((l))`

2) List the known and unknown quantities.

Sample: citric acid.

Volume: 20.0 mL = 0.0200 L

Molarity: unknown.

Base: NaOH.

Volume: 18.4 mL = 0.0184 L

Molarity: 0.100 M

3) Moles of NaOH that reacted.

`M=\frac{mol\text{ }NaOH}{Volume\text{ }(L)}`
`mol\text{ }NaOH=(0.100\text{ }M)*(0.0184\text{ }L)=0.00184\text{ }mol\text{ }NaOH`

4) Convert moles of NaOH to moles of H3C6H5O7.

The molar ratio between NaOH and H3C6H5O7 is 3 mol NaOH: 1 mol H3C6H5O7.

`mol\text{ }H_3C_6H_5O_7=0.00184\text{ }mol\text{ }NaOH*\frac{1\text{ }mol\text{ }H_3C_6H_5O_7}{3\text{ }mol\text{ }NaOH}=0.0006133\text{ }mol\text{ }H_3C_6H_5O_7`

0.0006133 mol H3C6H5O7 reacted.

5) Find the molarity.

Sample: citric acid.

Volume: 0.0200 L

Molarity: 0.0006133 mol.

`M=\frac{mol\text{ }H_3C_6H_5O_7}{L\text{ }of\text{ }solution}`
`M=\frac{0.0006133\text{ }mol}{0.0200\text{ }L}=0.030667\text{ }M`

The concentration of citric acid (H3C6H5O7) is 0.0307 M.

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