Which of the following reactions results in a decrease in entropy? 2so2 (g) + o2 (g) yields 2so3 (g) 2nh3 (g) yields n2 (g) + 3h2 (g) 2h2o2 (aq) yields 2h2o (l) + o2 (g) nahco3 (aq) + hcl (aq) yields nacl (aq) + h2o (l) + co2 (g)

Option (a) is the correct answer.

Explanation:

Entropy is defined as the degree of randomness of a substance.

For example, gases have more entropy as compared to liquids because molecules a gas have more kinetic energy due to which they move rapidly.

Also, when more number of moles are formed a chemical reaction then it means entropy has increased. But when there are less number of moles formed then it means there is a decrease in entropy.

Thus, we can conclude that the reaction results in a decrease in entropy as 3 moles is giving 2 moles.

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.