Radioactive decay question 6 options: is a spontaneous process. occurs when an unstable nucleus loses energy. does not require any input of energy. all of the above

The correct answer is all of the above.  

Nuclear or radioactive radiation or radioactive decay refers to the procedure by which an unstable atomic nucleus loses energy in the form of mass in its rest frame by discharging radiation like a beta particle, alpha particle, or a gamma ray. A substance comprising such unstable nuclei is regarded as radioactive. The process does not need any input of energy.  

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2

a is the correct answer