Compared to the mass and the penetrating power of an alpha particle, a beta particle has(1) less mass and greater penetrating power
(2) less mass and less penetrating power
(3) more mass and greater penetrating power
(4) more mass and less penetrating power

Answer is (1) - less mass and greater penetrating power.

Alpha particle is a ₂⁴He nucleus while beta particles are electrons. Hence, the mass of alpha particle is greater than the mass of beta particle. But, the penetrating power is higher in beta particle than alpha particle. Alpha particles can be blocked by few papers but beta particles can go through those papers.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)