# Chemistry

What is the sign of the entropy change for the following reaction, which is the principal process taking place when mortar hardens?
Ca(OH)2(s) + CO2(g) ---> CaCO3(s) + H2O(l)

Would the sign of entropy be negative since a solid and gas yields a solid and what does it mean by principal process?

1. 👍
2. 👎
3. 👁
1. I assume principle means that there may be intermediate reactions but what is shown is the overall reaction. I agree with you that delta S probably is negative and for the reason you cite. You don't mention the water but that is a liquid and S is lower for liquids than gases.

1. 👍
2. 👎
2. From experience, I can say it's negative. Most - if not all - reactions in which an adhesive, glue, cement or whatever you wanna call it hardens, it will be exothermic and entropy goes down. I also asked my chem teacher few months back about that, she said that's pretty much the case. Since the glue becomes more stable and lowers its entropy. Principal process could be what DrBob said, or/and it could also mean there may be completely different reactions going on.

1. 👍
2. 👎

## Similar Questions

1. ### CHEM

Calculate ΔSfus and ΔSvap for HF. Determine the entropy change when 7.60 mol of HF(l) freezes at atmospheric pressure. I already calculated ΔSfus as 24.103 J/k*mol and ΔSvap as 86.07 J/K*mol....These are correct (I checked

2. ### chemistry

2C2H2(g) + 5O2(g)→4CO2(g) + 2H2O(g) a. Determine the enthalpy change for the reaction. ΔH = (4(-393.5)+ 2(-241.8)) – (2(227) + 5(0)) The enthalpy change is -2511.6. b. Determine the entropy change for the reaction. ΔS =

3. ### Chemistry

If delta H°rxn and delta S°rxn are both positive values, what drives the spontaneous reaction and in what direction at standard conditions? The spontaneous reaction is a)enthalpy driven to the left. b)entropy driven to the

4. ### chemistry

Calculate enthalpy change of reaction for the combustion of gaseous ethanol. C2H5OH + 3O2 >> CO2 + 3H2O. Using standard molar enthalpies of formation. C2H5OH -235.3 ( it's negative sign) CO2 -393.5 H2O -241.8 (1) Calculate the

1. ### Chem

For the reaction, 3C2H2(g) ===> C6H6 at 25°C, the standard enthalpy change is -631 kJ and the standard entropy change is -430 J/K, Calculate the standard free energy change (in kJ) at 25°C. What is the formula that relates

2. ### chemistry

What is ΔH in the equation ΔG = ΔH - TΔS? A. The change in specific heat between the products and the reactants B. The change in enthalpy between products and reactants in a reaction C. The change in entropy between products

3. ### chemistry

As an ionic solid dissolves in water, the temperature of the solution increases. What best describes the enthalpy and entropy of the solution? A. The enthalpy change is negative, and the entropy decreases. B. The enthalpy change

4. ### Physics

A 298.0 kg block of ice at 0 C is placed in a large lake. The temperature of the lake is just slightly higher than 0 C, and the ice melts. What is the entropy change of the ice (in kJ/K)? What is the entropy change of the lake (in

1. In which of the following processes would the entropy of the system increase? a. A liquid forming from a gas. b. A solid forming from a gas. c. The number of gas molecules increasing during a chemical reaction.

2. ### Chemistry

C2H2(g) + 2 H2(g)--> C2H6(g) Information about the substances involved in the reaction represented above is summarized in the following tables. Substance/ So (J/mol∙K) /∆Hºf (kJ/mol) C2H2(g) / 200.9 / 226.7 H2(g) / 130.7 / 0

3. ### chemistry

What is the sign of the entropy change in eaech chemical reaction? a) N2O4(g)--> 2NO2(g) b) PCl3(g) + Cl2(g) --> PCl5(g) c) 2 Al(s) + 3/2 O2(g) --> Al2O3(s) d)N2(g) + 3H2(g) --> 2 NH3(g) e) S(s) + O2(g) --> SO2(g)

4. ### chemistry

For which of the reactions listed below will Gibbs free energy always be negative? A. An exothermic reaction that increases in entropy B. An endothermic reaction that decreases in entropy C. An endothermic reaction that increases