BR Thermochemistry #66

[Sonyfan08]

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In the passage it tells you that 10 gram of CaCl2 will raise 100 ml of water by 18 degrees celcius. The question asked, what is the highest temp reached after 40 grams of CaCl2 are added to 200 ml of water at 20 degrees celcius.

The answer just says that 40 grams of CaCl2 added to 200 ml of water will raise it 36 degrees. I don't quite follow that logic. Can someone explain it to me in more depth? Why is it 36 degrees and not 72?

Thank you so much

 

[vayntraubinator]

Dimensional Analysis?

10gCaCl2 raises 100mL of water by 18C.

10g CaCl2 raises 200mL of water by 9C.

Thus we now do:

40gCaCl2( 9 C/10g CaCl2) = 4 * 9 = 36C increase in Temperature

 

[apex954]

In the passage it tells you that 10 gram of CaCl2 will raise 100 ml of water by 18 degrees celcius. The question asked, what is the highest temp reached after 40 grams of CaCl2 are added to 200 ml of water at 20 degrees celcius.

The answer just says that 40 grams of CaCl2 added to 200 ml of water will raise it 36 degrees. I don't quite follow that logic. Can someone explain it to me in more depth? Why is it 36 degrees and not 72?

Thank you so much

Because you increased the volume to 200 from 100mL, the change in temperature will decrease by a factor of two...so instead of 72 degrees, it will change by 36 degrees Celsius.