The question is incomplete:
Complete question is
The most efficient way to determine whether a reaction is an exothermic chemical
reaction is to use —
A) an oxygen probe
B) a temperature probe
C) a pressure probe
D) a pH probe
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Answer:
Reaction is said to be exothermic in nature, if heat is evolved from the system. The resultant product formed is more stable. Since, during exothermic reaction, heat is given out be the system, temperature of system will increase. Hence, temperature is the probe to determine exothermic reaction.
Thus, correct answer is option B) a temperature probe
A is the correct answer. A combustion reaction creates carbon dioxide and water. A is the only answer choice were carbon dioxide and water are made.
Answer:
4:5
Explanation:
Let x represent the fraction of the mix that is hot water. Then the temperature of the mix is ...
60x +15(1-x) = 40·1
45x = 25 . . . . . . . . . subtract 15
x = 25/45 = 5/9 . . . divide by the coefficient of x
This is the fraction that is hot water, so the fraction that is cold water is ...
1-5/9 = 4/9
The ratio of cold to hot is ...
cold : hot = (4/9) : (5/9) = 4 : 5
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<em>Additional comments</em>
The problem assumes that the energy contained in a given mass of water is proportional to its temperature. That is almost true, sufficiently so that we can reasonably use that approximation.
If heat loss is figured into the problem, then additional information is needed regarding the energy content of water at temperatures in the range of interest. That is not provided by this problem statement, so we have ignored the heat loss.
