Chem 401 Discussion workshop #2 Name 4 For each of the following sets of conditi

Question

Chem 401 Discussion workshop #2 Name 4 For each of the following sets of conditions, predict the condions of spontaneity by placing a mark appropriate box. Always Spontaneous Only at Low Only at High Nevr Temp.- 5. Calculate AG (in kJ) for the following reaction at 25°C using the data in the table to the right. NO2m) 33.18 240.06 N 11.10 304.29 6. Is the previous reaction driven by enthalpy or entropy change? 7. A student wishes to determine the heat capacity of a coffee-cup calorimeter. After she mixes 100.0g fwater at 58.5°C with 105.0g of water already in the calorimeter at 22.8°C, the final temperature of the water is 39.7·The specific heat of water is 4184 J/g °C Calculate the heat capacity of the calorimeter, C', in Jc Remember that qsystem =-qs-mounding, We will treat the water added to the calorimeter as the system and the calorimeter and the water in it as the surroundings. This can therefore be re-written as: qwater addod to calorimeter) water in calorimoter) +Qeslorimetert) -((m)(c)(AT) Jeweier.dded i. ainmeter)-[(m)(c)(AT),w.m·c_kr) + C.(AT) (calarimetr) Note: This is how the calorimeter constant for this week 's experiment was calculated

Explanation / Answer

This is about the application of the gibbs energy equation

G = H – T*S

G is gibbs

H is enthalpy

T is temperature

S is entropy

1. H > 0

S > 0

The Gibbs energy must be negative in order to be spontaneous so according to this, this first part will only be spontaneous at high temperatures

G = H - T*S

2. This will be non spontaneous, the equation will always be positive

3. H > 0 and S < 0, this will always be spontaneous

4. H<0 and S < 0 , this will be spontaneous only at low temperatures

The second part

Calculate the enthalpy of reaction with

H rxn = H products - H reactants

H products = n products * Hformation

H reactants = n reactants * Hformation

H rxn = 11 100 - 2*33180 = -55 260 J / mole, it is important to change KJ to joules

The same thing goes for entropy

S rxn = S products - S reactants

Srxn = 304.29 - 2 * 240.06 = -175.83 J / mole

Gibbs rxn = H - TS

Gibbs rxn = -55 260 - 298.15*-175.83 = -2836.2855 Joule / mole or -2.836 KJ / mole

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