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# Chemistry Practical - small question watch

1. How would you perform the calculation ?

Let us assume that the temperature FALL was 3 degrees when 6g of NH4Cl was added to 100cm3 of water in a beaker.

Is it a simple application of Q=mct ?
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2. (Original post by Ari Ben Canaan)
How would you perform the calculation ?

Let us assume that the temperature FALL was 3 degrees when 6g of NH4Cl was added to 100cm3 of water in a beaker.

Is it a simple application of Q=mct ?
yes, but units have to be right, and also the value of mass you used is usually taken as

mass of solid + mass of solution.

your solution is water, and density of water is 1 g per cm cube, so 100 cm cube = 100 g.

hope that makes sense!
3. (Original post by shengoc)
yes, but units have to be right, and also the value of mass you used is usually taken as

mass of solid + mass of solution.

your solution is water, and density of water is 1 g per cm cube, so 100 cm cube = 100 g.

hope that makes sense!
The markscheme says that candidates should simply multiply 430 by their change in temperature (6 in my case). How and why ?

Also where did this 430 come from ?
4. Oh, wait.... 4.3*100 = 430 * change in temp.... Ah, I see.
5. Another question.

This is part of the same experiment and is actually the very next question after the part discussed earlier.

Assume the heat capacity of the beaker is Lambda

I know that I have to add the Change in heat energy of the solution + the change in heat energy of the beaker.

However, I only have the HEAT CAPACITY of the beaker. How do I convert this to Change in heat energy ??
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6. (Original post by Ari Ben Canaan)
Another question.

This is part of the same experiment and is actually the very next question after the part discussed earlier.

Assume the heat capacity of the beaker is Lambda

I know that I have to add the Change in heat energy of the solution + the change in heat energy of the beaker.

However, I only have the HEAT CAPACITY of the beaker. How do I convert this to Change in heat energy ??
Look at the units of heat capacity - it should give you a big clue...
7. (Original post by charco)
Look at the units of heat capacity - it should give you a big clue...
Multiply heat capacity by my temperature change ? Is it that simple ?

If so, what is the reasoning besides the argument in terms of homogenity and base units ?
8. (Original post by Ari Ben Canaan)
Multiply heat capacity by my temperature change ? Is it that simple ?
yup, it's that simple...

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