Which amount of sodium hydroxide would react exactly with 4.80 g of a triprotic acid, H3X\text{H}_3\text{X}H3X (Mr=192M_{\text{r}} = 192Mr=192)?
250 cm3250\text{ cm}^3250 cm3 of 0.20 mol dm−3 NaOH(aq)0.20\text{ mol dm}^{-3}\ \text{NaOH(aq)}0.20 mol dm−3 NaOH(aq)
100 cm3100\text{ cm}^3100 cm3 of 0.25 mol dm−3 NaOH(aq)0.25\text{ mol dm}^{-3}\ \text{NaOH(aq)}0.25 mol dm−3 NaOH(aq)
150 cm3150\text{ cm}^3150 cm3 of 0.50 mol dm−3 NaOH(aq)0.50\text{ mol dm}^{-3}\ \text{NaOH(aq)}0.50 mol dm−3 NaOH(aq)
250 cm3250\text{ cm}^3250 cm3 of 0.90 mol dm−3 NaOH(aq)0.90\text{ mol dm}^{-3}\ \text{NaOH(aq)}0.90 mol dm−3 NaOH(aq)