How many moles of CsOH does it take to react with 0.782 moles of H2SO4 in 2 CsOH + H2SO4 ---> Cs2SO4 + 2 H2O ?

The equation, 2CsOH + H2SO4 -----> Cs2SO4 + 2H2O tells you that for every mole of sulfuric acid used in this reaction 2 moles of cesium hydroxide is needed. So, if you start with 0.782 moles of sulfruic acid you would need 2X as much cesium hydroxide. Or, 0.782 moles H2SO4 * 2CsOH. Your answer then is 1.56 moles of CsOH is needed to react with 0.782 moles of H2SO4.