Question

Can someone explain how to do calorimeter equations?

Answer 1

post an example

Answer 2

when 1.00 L of 1.00 M Ba(NO3)2 solution at 25.0C is mixed with 1.00 L of 1.00 M Na2SO4 solution at 25C in a calorimeter, the white solid BaSO4 forms and the temperature of the mixture increases to 28.1C. Assuming that the calorimeter absorbs only a negligible quantity of heat, that the specific heat capacity of the solution is 4.18 J/C g and that the density of the final solution is 1.0 g/ml, calculate the enthalpy change per mole of BaSO4 formed.

Answer 3

so for the enthalpy change, you're only concerned with the initial temp (25 C), the final temp (28.1 C), the mass of the solution and the heat capacity of the solution; since the formula is: dH=m*Cp*dT

Answer 4

the mass of the solution, use the density,

density=mass/volume -> 1.0 g/ml = mass/ 2000 mL

mass = 2000 g

now plug it in: dH=(2000 g)*(4.18 J/C g)*(28.1C-25C)= 25916 J =26 kJ

so far so good?

Answer 5

it should say "find the mass.."***

Answer 6

wait so how do you make the joules into kilojoules again?

Answer 7

1 kJ = 1000 J

so to go from J to kJ divide by 1000

Answer 8

ahhhhh. thanks a lot! (:

Answer 9

no problem ! do you know how to find dH per mole of BaSO4 from here?

Answer 10

oh yeah actually no lol..

Answer 11

you would find the moles of BaSO4 produced from the reaction using the molar ratios:

Ba(NO3)2 + Na2SO4 -> BaSO4 + 2NaNO3

i'm gonna take a shortcut since all the numbers are 1 and say moles of BaSO4 = 1 mole


now you would divide the dH by moles of BaSO4, which gives you 26 kJ/mol

Answer 12

so basically it would end up being 26 again?

Answer 13

only because the moles of BaSO4 formed were 1.

if it was like 0.5 moles, the it'd be 26 kJ/0.5 moles = 52 kJ/mol

Answer 14

ahhh okay, so the enthalpy change is 26 kj/mol?

Answer 15

yep

Answer 16

thanks a lot! you were super helpful!!

Answer 17

no problem! hope that made things a bit clearer

Answer 18

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