Chemistry, 13.11.2019 06:31 GoAheadAndSmileToday

Calculate kcal for a calorimeter using the following data: temperature of hot water bath 36.2°c temperature of cold water bath 23.4 °c final temperature upon mixing 5.00 ml samples 28.7 °c

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Answer from: Tcutety

Answer : The value of $K_{cal}$ for a calorimeter is 8.68J/^oC

Explanation :

First we have to calculate the mass of water.

As we know that the density of water is 1 g/mL. The volume of water is 5.00 mL.

$Density=\frac{Mass}{Volume}$

$Mass=Density\times Volume=1g/mL\times 5.00mL=5.00g$

Now we have to calculate the heat lost by the hot water.

Formula used :

$Q_1=m\times c\times \Delta T$

or,

$Q_1=m\times c\times (T_2-T_1)$

where,

Q₁ = heat lost by hot water = ?

m = mass of water = 5.00 g

c = specific heat of water = 4.184J/g^oC

T_1 = initial temperature = 36.2^oC

T_2 = final temperature = 28.7^oC

Now put all the given value in the above formula, we get:

$Q_1=5.00g\times 4.184J/g^oC\times (28.7-36.2)^oC$

Q_1=-156.9J

Heat lost by the hot water is 156.9 J and the negative sign indicate that the heat is lost or released.

Now we have to calculate the heat gained by the cold water.

Formula used :

$Q_2=m\times c\times (T_2-T_1)$

where,

Q₂ = heat gained by the cold water = ?

m = mass of water = 5.00 g

c = specific heat of water = 4.184J/g^oC

T_1 = initial temperature = 23.4^oC

T_2 = final temperature = 28.7^oC

Now put all the given value in the above formula, we get:

$Q_2=5.00g\times 4.184J/g^oC\times (28.7-23.4)^oC$

Q_2=+110.9J

Heat gained by the cold water is 110.9 J and the positive sign indicate that the heat is gained or absorbed.

Now we have to calculate the difference between heat lost and heat gained that is equal to the heat gained by calorimeter.

Q=Q_1-Q_2=156.9J-110.9J=46.0J

Now we have to calculate the $K_{cal}$ for a calorimeter.

$K_{cal}=\frac{Q}{\Delta T{cold}}$

$K_{cal}=\frac{46.0J}{(28.7-23.4)}=8.68J/^oC$

Therefore, the value of $K_{cal}$ for a calorimeter is 8.68J/^oC

Answer from: Quest

The answer to your question really depends on three things: how much water you have, how cold it is to start out, and how cold the things around it are. water actually freezes when it gets to 32 degrees fahrenheit (0 degrees celsius), but the time it takes to get there may be different. let's start with the first. if you take two glasses, and fill one with a tiny bit of water, and the other about halfway, then put them both in the freezer, the one with less water will freeze first (you can try this at home, but i recommend using plastic cups and not glass ones). now let's move on to the second part. let's say you have two glasses, and you fill one with really cold water that has been in the refrigerator, and the other with really hot water from the sink. if you put both of them in the freezer, the one that started out colder will freeze first. for the third part, let's imagine that you have two glasses with the same amount of water in them, and the water is at the same temperature. imagine putting one outside on a really really cold day in georgia, and having a friend in alaska put one outside on the same day. since it would be so much colder in alaska, the glass of water there would freeze before yours. so, if you took a tiny bit of really cold water in a glass, and put it outside on a cold day in alaska, it would freeze a lot faster than a big glass of hot water outside on a cold day in georgia.

Answer from: Quest

50.23 i believe is correct but don't quote me on that.

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