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Naphthalene is an organic compound that has a strong mothballodor and is a common ingredient in moth repellants. suppose that amass of 2.35 of naphthalene is measur...

Question

Naphthalene is an organic compound that has a strong mothballodor and is a common ingredient in moth repellants. suppose that amass of 2.35 of naphthalene is measured and placed inside a bombcalorimeter. the initial temperature of the 1.5 kg of water in thecalorimeter surrounding the bomb is 21.3. the weighed sample ofnaphthalene is then combusted. calculate the final temperature ofthe water in units of C. Use Swater= 4.184 J/gC. Balanced chemicalequation for combustion of naphthalene is C10H8 +

naphthalene is an organic compound that has a strong mothball odor and is a common ingredient in moth repellants. suppose that a mass of 2.35 of naphthalene is measured and placed inside a bomb calorimeter. the initial temperature of the 1.5 kg of water in the calorimeter surrounding the bomb is 21.3. the weighed sample of naphthalene is then combusted. calculate the final temperature of the water in units of C. Use Swater= 4.184 J/gC. Balanced chemical equation for combustion of naphthalene is C10H8 + 12 O2 -> 10 CO2 + 4 H2O H= -5157 kj/mol



Answers

Mothballs are composed primarily of the hydrocarbon naphthalene (C10H8). When 1.025 g of naphthalene burns in a bomb calorimeter, the temperature rises from 24.25 C to 32.33 C. Find Erxn for the combustion of naphthalene. The heat capacity of the calorimeter, determined in a separate experiment, is 5.11 kJ>C.

Um

Okay, let's talk about kalorama tree. Here's the scenario, I've got some compound. Um, the C 10 H eight is called nap clean and I am using 1.25 g of this. And if I stick this in something called the bomb calorie emitter, Which is basically just some kind of bucket with water in it. And I have got a cup or a bucket inside of it. And I burned something like this Napfa Lean. So I burn you know, a gram of this. 1.025g of this. What happens is I changed the temperature in the, of the water in this calorie amateur From 24.25°C to 32.33°C.. So what is happening is this naps aligned is giving off energy and it's being absorbed by the water inside the calorie meter. So what I want to know is how much energy and we used delta E. How much energy was involved in this exchange. So normally we would say E. Or Q. It's the same thing. So Q. Is the amount of heat given off equals M. C. Delta T. And so the M. Is the mass. Um The sea is the specific heat and the delta T. Is the change in temperature. Now I have the mass of the naps line, I have the change in temperature for the water and I don't have a specific heat. So they do tell us in the scenario that the bomb calorie meter, the same bomb calorie meter was used in another experiment. And the heat capacity not the specific heat. The heat capacity was 5.11 kill the jewels to change for every degree Celsius that it was changed. Now it's not the same as specific heat. It's just to heat capacity. Uh huh. So with this information, we can actually skip the mass here because yeah, whatever you know we can encounter, we can figure in this heat capacity and then the change in temperature that this bomb kilogram eter had and that would tell us how much heat was absorbed by the bomb calorie meter. Which is also the same as the amount of heat that was given off by the nap flame. So basically we take our 5.11 killer jewels per degree Celsius and we multiply that by the change in temperature, Which in this case if you if you subtract 32.33 -24.25, you get 8.08°C.. So you would put that into the calculator and you get 41.3 will keep three sig figs since we have three sig figs for each of these numbers. So 41.3 Killah jewels of energy is what was released by the nap feeling and also absorbed by the bomb calorie meter. Yeah

This is just another example of Kalorama Tree. I've got the definition at the top justice in context for a learning if anyone's unsure of the topic we're working with here. So we're looking at a material that is composed of hydrocarbon. Napoli. We've got the formula front screen, so we have one point. Not 25 g of this that's burning, so the temperature increase goes from 24.25 to 32.33 We've got the heat capacity of the color ran into written there on while looking for the change in energy off reaction for the combustion up Napoli so fastly we need to calculate our Q of reaction. Using the equation on the screen gives the value of negative 41.28 kg jewels were then calculating moles. We have 7.99 times 10 to the minus three moles. Finally, we can calculate our change in energy or reaction, using the equation I've just highlighted, which gives us an answer off negative 5.2 times 10 to the three killer jewels, part mole

So we're giving information here about certain compound Maybelline. So C10 H eight and essentially it has an entropy of combustion of -5100. About 57 killer jewels promote And were given that we're going to use an initial mass of 0.0 1 5- zero g. Basically it changes the temperature a calorie meter By 0.21123 C. This is our first part. So remember that essentially for a cholera motor. Typically we define essentially a calorie emitter. We're not really interested in the mass of the calorie in there particularly. So we just define essentially a calorie miller constant or heat capacity basically for a calorie meter. Since basically the mass values already incorporated and then this is equivalent to the temperature change of the tower. So we're given information that the temperature changes 0.212 degrees Celsius. and one important point to no notice here is essentially since we're at constant pressure at constant pressure, normally delta H Is equivalent to delta U. Plus p delta v. Since we're at constant pressure, we can rewrite this as Q plus W plus p delta v. We know that work is to find this negative p delta V. So this crosses out. So at constant pressure only the entropy of combustion is equivalent to the heat transferred. And we're going to remember here, essentially we're gonna consider are calorie under as basically the surroundings per se. And then essentially the system itself is the content that's going to be combusted. So remember that essentially the queue of the system equals negative Q. Of the surroundings. So these are going to be important basically facts. So let's rewrite essentially the queue of the system is equivalent to negative 5557 kg per mole. But we only had a certain initial amount. But let's first write this in terms of surroundings And this is equivalent to 5157 kg per mole. But we only have this defined initial amount of are basically combustion compound. So we have to first consider that. So since our compound, let's rewrite at C10 a trade. So the queue of surroundings of 5,157 killer jewels promote. So let's remember that one mole of this compound we essentially only had. So one mole of this compound has how many grams. So let's first find that. So C 10 H. H. has a molar mass of about 128. So we had essentially 128 g For this. one more of compound. And in this case we only had, we need the grams and the moles cancel out to give us units basically. Uh we need units of energy in this case. So we only had 0.015-0 g in this case. So all our units cancel out. So this gives us confirmation. So we divide 50 5157 Divided by 128. Then multiply by 0.015- zero. And I'm just going to convert this into jewels for convenience. So this is equivalent to about 612 jewels. Which basically the calorie meter is the surrounding. So we can this is equivalent to the calories in their constant or the heat capacity of the calorie meter times the change in temperature. So in this case we can see that the change of temperature is 0.212°C, 612 divided by this. We can get a calorie meter constant is equivalent to about 2900 jules times inverse degrees Celsius. And this is our answer for part one. For the second part essentially we have basically information that the initial temperature of a calorie meter from part A. So we still are going to use the same, essentially calorie meter constant here Of 2900 was 22.102 degrees Celsius. What? We're deciding to use a different compound here, We're going to use octane. So the mass basically a 0.1040 g and were given that the heat combustion Is negative. 5,451 .4 kg promote. So once again we're going to have to do a conversion and we're since we're just going to assume that this is constant pressure again, So this is equivalent to queue of the system. So the key of the surroundings is the negative of that. So it's 5,457.4 killing tools promote. Now we have to do our conversion times one more Family g do we have? So eight times 12, 18. So that's 114 g per mole. And we have 0.1040 g. So, multiple, multiplying all this out, We can find that essentially Q. of the surroundings is about 5900 Uh 5980 in terms of jewels. And this is equivalent to a certain calorie meter constant that we defined before its 2900. So we divide this out and we find that the temperature change Is equivalent to one point about 1.72°C.. And now we can plug this essentially which is equivalent to final temperature minus initial. So our final temperature is equivalent to 1.72 Plus 22.10 to this gives us about 23.8-2 to create Celsius, and this is our final answer.


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