Homework Help: Chemistry(Please check)

Posted by Hannah on Friday, January 20, 2012 at 9:55pm.

1)A piece of metal with a mass of 5.50 grams changed in temperature from 25 to 55 degrees celsius when 21.3 joules was absorbed. What is the specific heat of the metal?

a)0.256
b)0.129
c)3.91
d) 7.75
e)0.710 Jg^-1 C^-1

I chose 7.75 because I did 5.50/21.3 and then multiplied by 30.

2)Which of the following equations represents a reaction for which the delta H can be called a standard enthalpy of formation, delta Hf?

a) FeO(s) + CO2(g) -> FeCO3(s)
b) 1/2 N2(g) + 2 O(g) -> NO2(g)
c) 2 Na(s) + Cl2(g) -> 2 NaCl(s)
d) Ba(s) + N2(g) + 3 O2(g) -> Ba(NO3)2(s)

e) more than one of the four equations above are standard enthalpies of formation.

I chose answer e.

Are these correct?

Chemistry(Please check) - DrBob222, Friday, January 20, 2012 at 10:51pm
1.
21.3 = mass x sp.h. x delta T
sp.h. = 21.3/(5.50*30) is not 7.75.

2.
I agree with d.
Chemistry(Please check) - Hannah, Saturday, January 21, 2012 at 12:28pm
Ok for number one i got 0.129 and for number 2 did you mean that my answer choice of e was correct or that just equation d is correct? Thank you for your help!!

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