Chemistry calculation help (1 Viewer)

[tam89]

How many grams of solid thallium at 248°C can be converted to liquid Tl at 351°C if 44.1 kJ of heat are applied?

Specific heat capacity of solid Tl = 0.503 JK-1g-1 (0.503JK^-1g^-1)
Specific heat capacity of liquid Tl = 0.717 JK-1g-1
Heat of fusion (per gram) = 20.9 Jg-1
Melting point of Tl = 303°C


A) 0.611 g

B) 452 g

C) 0.452 g

D) 0.531 g

E) 611 g

F) 531 g

 

[rama_v]

This question looks like its beyond the HSC sylabus but here's the general formula for these questions:

Q = mcΔT + mL_v , where L_v is the latent heat of fusion in this case.

There are a number of possibilities in these heat questions, however here they want to know how many grams of Thallium can be completely converted into liquid. The first term in the following equation is the energy required to heat up the solid Tl to melting temperature, the next is the energy required to break the Tl bonds and convert the Tl to liquid, and the final term is the energy required to increase the temperature of the liquid Tl.


Q = mc_solidΔT_melt + mL_fusion + mcΔT_liquid

44100 = m(0.503)(303-248) + m(20.9) + m(0.717)(351-303)

Solving for m, we get m = 531.4 g so the answer isF