Ice-cream Posted May 15, 2005 Share Posted May 15, 2005 Can any1 help me with this? In a coffee-cup calorimeter, 50ml of 0.1M AgNO3 and 50ml of 0.1M HCl are mixed to yield the following reaction: Ag+(aq) + Cl-(aq) --> AgCl(s) The 2 solutions were initially at 22.6 degrees C and the final temperature is 23.4 degrees C. Calculate the heat that accompanies this reaction in kJ/mol of AgCl formed. Assume that the combined solution has a mass of 100g and a specific heat capacity of 4.18 J/degrees C g. I used q = ms(detaT) = 100 x 4.18 x 0.8 = 334.4J. I then thought since there are 0.01 mols altogether, then that means for 0.01 moles it's 334.4J, so 1 mole is 33440J. but that's the wrong answer. I think it's the moles part that's wrong - i'm not sure if it's ok to find moles of AgNO3, moles of HCl and then just add them up... then answer's -66kJ/mol Link to comment Share on other sites More sharing options...
dash00 Posted May 21, 2005 Share Posted May 21, 2005 Im just a highschool student myself so im sure people around here know more than i do but the mole ratio is 1:1 --> 1 i thought. so you do not add the 0.05L*0.1 M = 0.005 moles together, i believe. To get the molar heat of reaction, try 334.4 /0.005 ! hope thats a help, maybe someone else can explain it more clearly to you than i could the reason for doing this. Link to comment Share on other sites More sharing options...
Martyn Posted June 6, 2005 Share Posted June 6, 2005 q=mc(delta T) q= 100 X 4.18 X 0.8 q= 334.4 J (0.334 KJ) moles= (Molarity X volume) / 1000 moles = 0.005 so, 0.3344 / 0.005 = 66.88 therefore, -66.88 KJmol-1 (delta H is negative as heat is given out so it is exothermic) Link to comment Share on other sites More sharing options...
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