For which reaction is delta Ssys > 0?
A) CH4(g) + 2 O2(g) �¨ CO2(g) + 2 H2O(l)
B) NH3(g) + HCl(g) �¨ NH4Cl(s)
C) 2 NH4NO3(s) �¨ 2 N2(g) + O2(g) + 4 H2O(g)
D) HCl(aq) + NaOH(aq) �¨ NaCl(aq) + H2O(l)
dS is + (i.e., >0) when S products is greater than S for reactants.
A has 3 mols gas on the left and 1 on the right; therefore, dS decreases.
Remember S increases from solids to liquids to gases. Therefore, A and B can't be right.
To determine which reaction has a positive change in entropy (ΔSsys > 0), we need to consider the changes in the number of moles and the physical states of the reactants and products.
Entropy (S) is a measure of the disorder or randomness of a system. An increase in the number of particles or a change from a more ordered to a less ordered state generally results in a positive change in entropy.
Now, let's analyze each reaction:
A) CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)
In this reaction, there is a decrease in the number of moles of gas molecules. Since gases have more disorder compared to liquids, this reaction results in a decrease in entropy, and ΔSsys is less than zero (ΔSsys < 0).
B) NH3(g) + HCl(g) → NH4Cl(s)
In this reaction, we have a gas (NH3) and a gas (HCl) combining to form a solid (NH4Cl). This change involves a decrease in the number of particles and a transition from a more disordered state (gases) to a more ordered state (solid). Thus, this reaction also results in a decrease in entropy, and ΔSsys is less than zero (ΔSsys < 0).
C) 2 NH4NO3(s) → 2 N2(g) + O2(g) + 4 H2O(g)
In this reaction, we have a solid (NH4NO3) decomposing into gases (N2, O2, H2O). This decomposition increases the number of particles and leads to a more disordered state, resulting in an increase in entropy. Thus, this reaction has a positive change in entropy, and ΔSsys is greater than zero (ΔSsys > 0).
D) HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
In this reaction, we have two aqueous solutions combining to form a salt (NaCl) and water (H2O). While there is no change in the number of particles, there is a change from a more disordered state (solutions) to a less disordered state (solid and liquid). As a result, this reaction leads to a decrease in entropy, and ΔSsys is less than zero (ΔSsys < 0).
Therefore, the reaction for which ΔSsys > 0 is C) 2 NH4NO3(s) → 2 N2(g) + O2(g) + 4 H2O(g).