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    • Thread Starter

    You are provided with 50.0 cm3 of 0.200 mol dm−3 hydrochloric acid and a standard solution of NaOH and titration equipment and a solid which is believed to be calcium hydroxide. How would you calculate the relative formula mass by means of titration to determine whether this solid is calcium hydroxide. Please help with the calculations and the understanding behind the calculations, thanks.

    I wonder if calcium hydroxide is not there present in the titration how would we calculate? Did you want to find the Mr of NaOH?
    Also, is it allowed to measure the mass of the solid?
    • Thread Starter

    Hi yes so i went about this question firstly by calculating the mass of calcium hydroxide and found a value of 0.371g this was deduced from the information given about HCl. But however the acid obviously needs to be in excess for the titration to occur so we need less than 0.371g of Calcium Hydroxide. But then i am a little confused aabout how to calculate the number of moles of Calcium Hydroxide, at the start we originally have 5.00x10-3 but then apparently the number of moles of NaOH should be subtracted tfrom this value. I dont understand why this is, since it is the excess HCl that reacts with the NaOH.
    So in summary the bit i am just unsure with is why do we subtract the number of moles of NaOH from the original number of moles of Calcium Hydroxide??

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