[bpeck8]

Here is 1 trial i did in lab tonight. I need help on the appropriate significant figures in the final answers to be used.

Specific Heat of Unknown:

                                    Trial 1

Mass of cup                    1.89 g
Mass of cup + water       76.52 g
Mass of water                74.63 g
Mass of unknown            30.44 g
Temp. of water bath      100.2 C
Initial unknown Temp.    100.2 C
Initial water Temp.          21.3 C
Final Temp.                    27.6 C
SH water                        4.184 J/g C
T water                          ?
T unknown                      ?
SH unknown                    ?

My calculations:

mass of water = 76.52 g - 1.89 g
                    = 74.63 g

T water = |27.6 C - 21.3 C|
           = 6.3 C

T unknown = |27.6 C - 100.2 C|
               = 72.6 C

Q = (4.184 J/g C)(74.63 g)(6.3 C)
   = 2.0x10^3 J

SH unknown = 2.0x10^3 J / (30.44 g)(72.6 C)
                 = 0.9050 J/g C

Please correct me, i know i am wrong, just dont see it.

[JDeGra]

Why did you round to 2.0x10^3 J? You should keep as many digits until the end.  c= -1967.2J/30.44g (-72.6 C)    I got .89015 J/g C  3 sig figs~ 8.90 x 10^-1