1. A 2-mol sample of potassium chlorate decomposes to form potassium chloride an
ID: 556570 • Letter: 1
Question
1. A 2-mol sample of potassium chlorate decomposes to form potassium chloride and oxygen gas. The reaction was accomplished with release of 78.0 kJ heat. Write a balanced thermochemical reaction for this process.
2. To make a cup of coffee, you heated 0.175 kg of water to change the water temperature from 23.0 degrees C to 89.0 degrees C. Calculate the quantity of heat (J) required.
3. A 56.3-g sample of water was heated to 51.2 degrees C and added to 45.8 g of 20.3 degrees C of water in a calorimeter. Assume that no heat was lost to the surroundings including the calorimeter, calculate the final temperature o the resulting solution. Show Work!
Explanation / Answer
potassium chlorate decomposes to form potassium chloride and oxygen gas.
KClO3(s) + heat = KCl(s) + O2(g)
balance O
KClO3(s) + heat = KCl(s) + 3/2O2(g)
Q2.
Q = m*C*(Tf-Ti)
for water, Cp = 4.184J/gC
Q = (175)(4.184)(89-23)
Q = 48325.2 J
Q3
Qcold = -Qhot
56.3*4.184*(Tf-51.2) = -45.8*4.184*(Tf-20.3)
56.3/45.8(Tf-51.2) = (Tf-20.3)
-1.2292Tf + 1.2292*51.2 = Tf-20.3
Tf(1+1.2292) = 1.2292*51.2+20.3
T f= (1.2292*51.2+20.3)/(1+1.2292)
Tf = 37.33 °C
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