Question

consider the following reaction at 298k:

si (s) +2Cl2 (g) = sicl4(l)
calucfales delta s universe. express your answer in j with no decimal place

Answer 1

[AI-generated answer — Bot]

To calculate the delta S (entropy change) of the universe for this reaction, we need to find the entropy change of the system (delta S system) and the surroundings (delta S surroundings). Delta S universe is the sum of these two values.

First, let's calculate delta S system. We can do this by finding the standard entropy (S°) values for each substance in the reaction at 298 K and using the equation:

Delta S system = Sum(S° products) - Sum(S° reactants)

We will need the following standard entropy values at 298 K (values taken from standard entropy tables):

S° (Si) = 18.8 J/mol*K
S° (Cl2) = 223 J/mol*K
S° (SiCl4) = 311.7 J/mol*K

Now we can calculate delta S system using the stoichiometry of the reaction:

Delta S system = (1 * S° (SiCl4)) - (1 * S° (Si) + 2 * S° (Cl2))
Delta S system = (1 * 311.7 J/mol*K) - (1 * 18.8 J/mol*K + 2 * 223 J/mol*K)
Delta S system = 311.7 - (18.8 + 446)
Delta S system = -153.1 J/mol*K

Next, we need to calculate delta S surroundings. This can be done using the equation:

Delta S surroundings = - (Delta H system / T)

But we first need the enthalpy change of the reaction (delta H system). We can find this using standard enthalpies of formation (ΔHf°) values:

ΔHf° (Si) = 0 kJ/mol (since it's an element in its standard state)
ΔHf° (Cl2) = 0 kJ/mol (since it's an element in its standard state)
ΔHf° (SiCl4) = -657.7 kJ/mol

Now we'll use the equation for the enthalpy change of the reaction:

Delta H system = Sum(ΔHf° products) - Sum(ΔHf° reactants)

Delta H system = (1 * ΔHf° (SiCl4)) - (1 * ΔHf° (Si) + 2 * ΔHf° (Cl2))
Delta H system = (1 * -657.7 kJ/mol) - (1 * 0 kJ/mol + 2 * 0 kJ/mol)
Delta H system = -657.7 kJ/mol

Now we can find delta S surroundings:

Delta S surroundings = - (Delta H system / T)
Delta S surroundings = - ((-657.7 kJ/mol) / 298 K)

First, we convert kJ to J by multiplying by 1000:

-657.7 kJ/mol * 1000 = -657700 J/mol

Now, we calculate Delta S surroundings:

Delta S surroundings = -((-657700 J/mol) / 298 K)
Delta S surroundings = 2205.7 J/mol*K

Finally, we can find the entropy change of the universe:

Delta S universe = Delta S system + Delta S surroundings
Delta S universe = -153.1 J/mol*K + 2205.7 J/mol*K
Delta S universe = 2052.6 J/mol*K

So, the entropy change for this reaction at 298 K is approximately 2053 J/mol*K for the universe.