Which of the following chemical reactions has positive entropy change?
a. n2(g) + 3 h2(g) \longrightarrow ⟶ 2nh3(g)
b. br2(g) \longrightarrow ⟶ br2(l) n2o4(g)
c. \longrightarrow ⟶ 2 no2(g)
d. naoh(aq) + co2(g) \longrightarrow ⟶ nahco3(aq)

Explanation:

Entropy is the measure of randomness or disorder of a system. If a system moves from  an ordered arrangement to a disordered arrangement, the entropy is said to decrease and vice versa.

is positive when randomness increases and is negative when randomness decreases.

a)

4 moles of gas are converting to moles of gas, hence the entropy decreases.

b)

1 mole of gas is converting to 1 mole of liquid, hence the entropy decreases.

c)

1 mole of gas is converting to 2 moles of gas, hence the entropy increases.

d)

1 mole of gas is disappearing , hence the entropy decreases.

Thus has positive entropy change.

altitude, density, pressure

air gets less dense the higher the altitude and also the air pressure is less as altitude rises.