Is the following reaction endothermic or exothermic?
C3H8 + 5 O2 --> 3 CO2 + 4 H2O
H= -2200 kJ
endothermic
exothermic
exothermic
You are performing an experiment that uses 113Ag. 113Ag is radioactive, decays by beta-minus emission and has a half-life of 5.3 hours. It requires 31.8 hours to ship the material from the warehouse to your laboratory. How many grams should you order if the experiment requires that you have 40 grams to begin the experiment?
2.40 x 102 g
0.625 g
2.56 x 103 g
6.67 g
The amount of time it takes for the material to be shipped to the laboratory is much longer than the half-life of 113Ag, which means that a significant amount of radioactive decay will occur during shipping. To determine the amount of 113Ag that should be ordered to ensure that there is enough for the experiment, we can use the radioactive decay equation:
N = N0(1/2)^(t/T)
where:
N0 = initial amount of 113Ag
N = final amount of 113Ag (after shipping)
t = time elapsed during shipping (31.8 hours)
T = half-life of 113Ag (5.3 hours)
We can solve for N0 by plugging in the given values:
40 g = N0(1/2)^((31.8)/(5.3))
N0 = 2.56 x 10^3 g
Therefore, the amount of 113Ag that should be ordered is 2.56 x 10^3 g. Answer: 2.56 x 10^3 g.
To determine if the reaction is endothermic or exothermic, we need to consider the enthalpy change (ΔH) of the reaction. If ΔH is positive, the reaction is endothermic, while if ΔH is negative, the reaction is exothermic.
In this case, the given enthalpy change (H) is -2200 kJ, which means that the reaction releases energy. Since the enthalpy change is negative, the reaction is exothermic.