Question

What mass of HC2H3O2 ( acetic acid) must be dissolved in 800.0 g H2O to produce a 6.25 m solution?

Answer 1

Answer: mass of HC2H3O2 = 300.25 grams.

Explanations and Calculations :

GIVEN

• 800g of H2O > 800/1000= ,0.8 Litres of water

,

• Concentration = 6.25 M

,

• Molar mass acetic acid = 60.05g/mol

(i) Calculate number of moles :

$\begin{gathered} Concentraion\text{ = moles /volume } \\ \therefore Moles\text{ = Concentration * volume } \\ \text{ = 6.25 mole/L * 0.8 L} \\ \text{ = 5moles } \end{gathered}$

( ii) Calculate mass of CH3COOH or ( HC2H3O2)

$\begin{gathered} Mas\text{s = \lparen moles * Molecular mass \rparen} \\ \text{ = \lparen5mol* 60.05g.mol}^{-1}) \\ \text{ =300.25 grams } \end{gathered}$

Therefore mass of acetic acid = 300.25 grams