Lava at TH = 1025° C emerges from a volcano. A mass m = 65 kg of this lava flows at a constant velocity of v = 0.38 m/s losing Q = 16500 J of heat every second to the surroundings. The lava flows a distance of 250 m before reaching the ocean. Assume that the temperature of the surroundings, Tsurr = 29° C is unaffected by the cooling of the lava. A) Calculate how long t in seconds it takes before this mass of lava reaches the ocean. B) Calculate the amount of heat Ql in joules lost to the surroundings before this mass reaches the ocean. C) If the specific heat capacity of the lava in this process is c = 840 J / kg °C, calculate the temperature of this mass of lava T in celsius just before it reaches the ocean. D) Calculate entropy change of the surroundings ΔSsurr in J / K while the lava was moving toward the ocean. E) Calculate the change in the entropy of the lava ΔS in joules per kelvin while the lava was moving toward the ocean.

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.