From the equation q=mCΔT, set the q of copper = to q of water,
So --- mCΔT(copper)=mCΔT(water).
mass (Cu - copper) = 38g
mass (H2O - water) = 15g
C (H2O) = 4.184 J/g*C
ΔΤ (H2O) = 33-22 = 11*C
ΔΤ (Cu) = 33-80 = -47*C (the final temp is the same for both materials - thermal equilibrium)
C (Cu) = ?
So --- 38(-47)C[Cu]=15(4.184)(11)
--- C[Cu]=690.36/(-1786) = 0.3865 J/g*C, or 0.39 in 2 sig figs. (The negative goes away, because specific heats are usually positive)
Answer:
16 minutes
Explanation:
First, we need to calculate the amount of heat needed to cool the beef stew:
Q = mcΔT
Where <em>m</em> is the mass, <em>c</em> is the heat capacity and <em>ΔT</em> is the variation of the temperature.
Q = 10x4x(40 - 90)
Q = -2000 kJ
So, the beef stew needs to lost 2000 kJ to cool.
With the initial temperature at 90ºC, the rate of cooling(r) will be:
r = 1.955x(90 - 25)
r = 127.075 kJ/min
So, to lose 2000 kJ, will be necessary:
t = Q/r
t = 2000/127.075
t = 16 minutes
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An example of a land form from magma is B. Lava Plateau.
The oxidation state of Mn2 is 2+
