Astudent performs a reaction twice. in the second trial, he increases the temperature of the reaction and notes that the reaction happens more quickly. the student concludes that this means the reaction was endothermic. what is wrong with the student's reasoning? a. higher temperature increases reaction rates for both endothermic and exothermic reactions. b.an endothermic reaction would not speed up at higher temperatures. c.temperature does not affect the rate of a reaction. d.the higher temperature in the second trial actually lowered the activation energy of the reaction.

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

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