Using the pKa value of 476 for ethanoic acidcalculate the va

Using the pK_a value of 4.76 for ethanoic acidcalculate the value for K_a for ethanoic acid. What massof sodium ethanoate needs to be present in 1.00 dm³ of asolution of 0.500mol dm^-3 ethanoic acid to give a buffersolution with a pH pH 5.0? What would be the resulting pH if twiceas much sodium ethanoate was dissolved in 1.00 dm³ ofthe 0.500 mol dm^-3 ethanoic acid solution?