Homework 4C 13

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MaryBanh_2K
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Homework 4C 13

Postby MaryBanh_2K » Fri Feb 07, 2020 2:48 am

An ice cube of mass 50.0 g at 0.0 8C is added to a glass containing 400.0 g of water at 45.0 8C. What is the final temperature of the system (see Tables 4A.2 and 4C.1)? Assume that no heat is lost to the surrounding.

For this problem, I understand that we find the total heat for ice and total heat for water and then we equal the equations together to find final temperature since no heat is lost to the surroundings. This means we can make these equal to each other but give one a negative sign since heat lost by the water went to the ice. Which side, in this case, would have the negative sign when we equate the two total heats together, heat (ice cube) or heat (water). In other words, is it [heat (ice cube) = -heat (water)] OR [-heat (ice cube) = heat (water)] and why?

madawy
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Re: Homework 4C 13

Postby madawy » Fri Feb 07, 2020 10:03 am

I believe the negative sign would be given to the water, since the water is giving off its eat to melt the ice cube, which is absorbing the heat in order to change phases.

Katie Kyan 2K
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Re: Homework 4C 13

Postby Katie Kyan 2K » Fri Feb 07, 2020 5:33 pm

Yes I agree with the previous commenter that the negative sign should be given to the water since the water is releasing heat in order to melt the ice cube.

805373590
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Re: Homework 4C 13

Postby 805373590 » Fri Feb 07, 2020 6:56 pm

the heat lost by the ice is equal to negative the heat gained by the water. so the sign would go to water in liquid form.

Rebekah Alfred 1J
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Re: Homework 4C 13

Postby Rebekah Alfred 1J » Fri Feb 07, 2020 7:03 pm

The substance with a greater temperature (hotter) will be the one transferring heat to the substance with a lower temperature (colder), which is why the negative sign will be given to the water (which is losing its heat).

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Emma Popescu 1L
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Re: Homework 4C 13

Postby Emma Popescu 1L » Fri Feb 07, 2020 10:34 pm

For this question, why do we use the specific heat capacity of liquid water instead of ice?

Jasmine 2C
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Re: Homework 4C 13

Postby Jasmine 2C » Sun Feb 09, 2020 10:14 pm

Emma Popescu 1L wrote:For this question, why do we use the specific heat capacity of liquid water instead of ice?

we use the specific heat capacity of liquid water for ice because we're calculating the heat after it has been melted from solid to liquid

Sofia Barker 2C
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Re: Homework 4C 13

Postby Sofia Barker 2C » Sun Feb 09, 2020 11:49 pm

The ice is absorbing the heat given off by the water. We know that exothermic reactions have a positive delta H because they are taking in heat, whereas endothermic reactions have a negative delta H value because they release heat. We can use this same logic with this problem to conclude that the q of liquid water will be negative because it represents heat released or lost by the water.


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