sat_chen
It was pointed out that mass and energy are alternate aspects of a single entity called mass-energy. The relationship between these two physical quantities is Einstein's equation, E = mc2, where E is energy, m is mass, and c is the speed of light. In a combustion experiment, it was found that 10.965 g of hydrogen molecules combined with 87.000 g of oxygen molecules to form water and released 1.554 × 103 kJ of heat. Use Einstein's equation to calculate the corresponding mass change in this process,
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sat_chen
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how would you start the conversion would you do this |dw:1359337417354:dw|
sat_chen
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im really confused as to how to do this conversion although i thought i had this stuff down :(
sat_chen
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thats how i did the above conversion btw |dw:1359337550325:dw|
Azteck
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I haven't thoroughly studied physics yet. I think this is better off in the physics section. But I think you're meant to convert the mass into kg's first before doing anything else. And the kilojoules to joules.
sat_chen
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this if from my chemistry book all its asking to do is conversion
sat_chen
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the formula is given just have to apply it and i have no clue
Azteck
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1.554 × 103 kJ ?
Is it 1.554 x 10^3 kJ.
sat_chen
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yes
Azteck
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Okay.
sat_chen
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i converted it to J thats why its 1.554*10^6 in my attempt
Azteck
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SO it's this?
\[1.554\times 10^6 \times \frac{ kgm^x }{ s^x }\]
sat_chen
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ill post a print screen of the problem
sat_chen
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sat_chen
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sorry i should have probably posted the problem earlier
Azteck
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Okay, Do you have the correct answer? Like an answer sheet or something?
sat_chen
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no i cant get the solution it would be 0 points after that :)
sat_chen
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i can try random answer to see if it gives me hint
sat_chen
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i have 5 attempts to get it right
Azteck
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I got some weird number. I got
\[4.564\times 10^{13}\]
Azteck
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That's to 4 significant numbers
sat_chen
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ok im gonna try that see if its right
sat_chen
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nope
Azteck
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No it's not.
sat_chen
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not the right answer
Azteck
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Don't you have to find the mass of the water?
sat_chen
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no we dont
sat_chen
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we are just trying to do some conversion this is Chapter 2 should be some basic stuff
Azteck
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Wait mate. You're trying to find the change in mass?
sat_chen
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yes
sat_chen
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the question does say that :P
Azteck
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Man, heat of combustion keeps popping up in my head for some reason.
sat_chen
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so would you do something like mole so 12.096/1.008 and 96/16 and get the value in mole form
Azteck
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I'm not sure but it's worth a try. because heat of combustion is sort of what this experiment sort of is. Because you got your energy/heat released and then you got your mass changes and stuff.
sat_chen
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yea its nothing complicated like that i have just started to dip into basic chemisty
Azteck
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What year/grade is this?
sat_chen
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first year chemisty college not incredibly basic but 101
sat_chen
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so far we have just learned how to name basic stuff, learning to name polyatomic ions etc emperical formula stuff like that really easy stuff i aced all the other problem but this one is tripping me up
Mertsj
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Just plug into the equation E = mc^3. The energy is given, you know the speed of light. Calculate mass
Azteck
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Okay. I don't think I can help. I still have one year until universtiy/college. I'm afraid I can't help you.
Azteck
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@Mertsj got you covered.
sat_chen
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so would you |dw:1359339344388:dw|
sat_chen
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and square the speed of light
sat_chen
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then change from g to kg by dividing by 1000 or would you conver to mole
Azteck
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ANd then I think you might subtract what you get from the mass of the oxygen and hydrogen molecules...
sat_chen
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so heres what im doing right now since m = e/c^2
sat_chen
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first i change the 10.965/1.001 and 87/16 to convert it to mole
sat_chen
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then i divide 1554000/2.9*10^8
Mertsj
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E should be in joules, m in kilograms and c in meters per second
snapcracklepopz
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sorry to interrupt but can someone help me after you are done helping this person with their question please?
sat_chen
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i really am not getting this
Mertsj
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\[\frac{1.554\times 10^6}{(3\times 10^8)^2}=.1727 \times 10^{-10} kg\]
sat_chen
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yea ive done that before is that just it?
sat_chen
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then you convert from kg to g?
Mertsj
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Multiply by 1000
Mertsj
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That's what I think it is. Because the equation tells you how much mass is needed to produce that much energy.
sat_chen
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nope thats not it
sat_chen
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oops i messed up
sat_chen
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hold on i forgot to square
Mertsj
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\[.1727 \times 10^{-10}kg=.1727 \times 10^{-7}g = 1.727 \times 10^{-8}g\]
sat_chen
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yea but i ran out of turns and that was the answe r:(
sat_chen
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well thanks a lot for your help
Mertsj
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What was the answer?
sat_chen
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1.72*10^-8
Mertsj
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yep. I thought so.
sat_chen
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yea im gonna have to hit the books again and learn why i didnt get it thanks a lot
Mertsj
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yw