x CA Scientist Measures The X valentActivity do Riocator entsession e a Search R

Question

x CA Scientist Measures The X valentActivity do Riocator entsession e a Search References Review Topics Use the References to access important values if needed for this question. When a solid dissolves in water, heat may be evolved or absorbed. The heat of dissolution (dissolving) can be determined using a coffee cup calorimeter. In the laboratory a general chemistry student finds that when 10.79 gof CsBr(s) are dissolved in 115.70 g of water, the temperature of the solution drops from 24.40 to 21.28 oC. The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.77 JhoC. Based on the student's observation, calculate the enthalpy of dissolution of CsBr(s) in kJlmol. Assume the specific heat of the solution is equal to the specific heat of water kJ mol ution 2 mpte group attempts remainng

Explanation / Answer

Question 1.

m = 10.79 g f CsBr

m = 115.70 g of water

dT = 21.28-24.40 = -3.12 °C drop

note that we also hav ea calorimeter

Ccal = 1.77 J/°C

so.

Qgained = -Qlost

Qgained = Qcalorimter + Qwater

Qlost = Qrxn

-Qrxn = Qcalorimter + Qwater

Qrxn = n*HRxn

Qcalorimter = Ccal*dT

Qwater = m*Cp*dT

-n*HRxn = Ccal*dT +  m*Cp*dT

moles of CsBr = mass/MW = 10.79/212.81 = 0.050702 moles of CsBr

so

-0.050702 * HRxn = 1.77*(-3.12) + 115.7*4.184*(-3.12)

HRxn = -1515.879/-0.050702

HRxn = 29897.814 J/mol

HRxn = 29.89 KJ/mol

it is possitive, since it is ENDOTHERMIC

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