Consider a 67-g chunk of ice (∆Hfus = 6.0 kkJ/mol) in a beaker immersed in a water bath. To produce just enough heat to melt the ice, how many moles of solid NaOH (∆Hsoln = -445.1 kJ/mol) must you dissolve in the water bath?

Question

Consider a 67-g chunk of ice (∆Hfus = 6.0 kkJ/mol) in a beaker immersed in a water bath. To produce just enough heat to melt the ice, how many moles of solid NaOH (∆Hsoln = -445.1 kJ/mol) must you dissolve in the water bath?
Please show all work.

Thanks in advance.

bonjo · Answer

67g of ice is 67/18 = 3.72moles. 6.0kJ/mol means it takes 6.0 kJ to convert 1mole of solid ice into liquid water. so, for 3.72moles requires 3.72x6= 22.333kJ energy input.

the energy released is 445.1kJ/mol from NaOH. so 22.333kJ energy from NaOH must be used/provided..isn't it???..that means we are to find how many mole of NaOH is required to produce 22.333kJ..getting there???...we know that 1mole of NaOH releases 445.1kJ..How many moles are required to release 22.333kJ????

hope that helps..