Anonymous
Anonymous asked in Science & MathematicsChemistry · 1 month ago

Chemistry Homework, help please?

Given 354 mL of water at 24 ∘C in a perfectly heat-insulating container, how much ice at 0 ∘C (in grams) would have to be added to this water so that after the ice has melted, the overall temperature of the system has been lowered to 6 ∘C? (Assume the density of water is 1.0 g/mL. The heat of fusion for water is 6.02 kJ/mol. The specific heat of water is 4.18 J/(g⋅∘C).)   

I have tried to do this many times but I dont understand what im doing wrong

thanks

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  • 1 month ago

    Since we are assuming that the specific heat of water is constant, we can rephrase the question in a slightly simpler way: 

    How much ice at 0C would have to be added to water that started at 12C, so that the overall temperature of the system ends up at 0C but it's all liquid.

    The water loses (4.18 J/gC)(12 C)(354 g) = 17.757 kJ.

    How much ice will be melted?  (17.757 kJ)/(6.02 kJ/mol) = 2.95 moles = 53.1 grams.

    ************** Gonna check this in my own way below *****************

    (80 cal/g)(53.1 g) = around 4000 cal.  Will this bring 354 g of water from 12C down to 0C?  Yes.

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