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Thread: General Chem Thermochemistry Problems

  1. #1 General Chem Thermochemistry Problems 
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    Question 9: An iron skillet having a mass of 1.51kg is heated on a stove to 178 degrees Fahrenheit. If the skillet cools to room temperature at 21 degrees Celcius, calculate heat change for the skillet.

    Should I simply subtract 178 degrees C by 21 degrees C in order to get the enthalpy change?

    Question 10: An aluminum engine part having a mass of 440 g is found in a cold engine at 19.5 degrees C. If the combustion of fuel within the engine generates 75 kJ of heat, what's the final temperature of the engine part? Will the engine part melt under the strain?

    Would the first formula used by q=ms(change in T)? What other formulas are needed for question?


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  3. #2  
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    For the question nine, first thing you got to notice is that 178 is Fahrenheit and 21 is Celsius. As such, I advise you to transform both values into K.
    Second thing, it asks for a difference in heat, not temperature. As such, you have to calculate the amount of heat (or energy) that was set free in the process.
    As for the question ten, I'm not even sure what have you meant with your formula. The formula you require, both for tasks nine and ten, is is fact


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  4. #3  
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    Whoops..meant to type both in celsius for 9.

    Oh..and what does the c in the equation stand for?

    Thanks in advance.
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  5. #4  
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    Than we solved the first problem, still, the point stands. You can't simply subtract the temperatures. You got to find the Q difference.
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  6. #5  
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    Quote Originally Posted by Sindrato
    Than we solved the first problem, still, the point stands. You can't simply subtract the temperatures. You got to find the Q difference.
    Thank you sir.
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    c is the specific heat of the metal. It's the same as s in your version of the equation.
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  8. #7  
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    If so, Bunbury, I am sorry for mistake. In my country, Croatia, we use c for all the specific heats. And also, no need to address me as sir. I am 16 years old :-D
    Still, you are welcome.
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  9. #8  
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    Sindrato, there's nothing to apologize for. I was merely answering gottspieler's question. As far as I know c is the usual symbol for specific heat but maybe s is used in some countries.
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  10. #9  
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    Quote Originally Posted by Sindrato
    If so, Bunbury, I am sorry for mistake. In my country, Croatia, we use c for all the specific heats. And also, no need to address me as sir. I am 16 years old :-D
    Still, you are welcome.
    Well, you're a bright, respectable guy so you deserve to be called sir. :P I'd rather address you as such than an undeserving 40 year old.
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