HYS CH5,6 Thermodynamics and Kinetics Problem Solving

Question 1

why is this correct

Answer 1

all are gas, so we must look at moles
6 –> 7 moles
left (1 + 5) and right (3 +4)

Question 2

dissolution of sodium nitrate is an endothermic reaction. It is spontaneous at high temperatures because delta H is …

Answer 2

**positive and less than TdeltaS
**

endothermic means positive delta H (enthalpy)
to be spontaneous delta G (free energy) must be negative

pos delta H only possible when delta H is less than TdeltaS

if it were > TdeltaS, it would be nonspontaneous as delta G would be positive

Question 3

what does + and - delta G mean?

Answer 3

+ … endothermic (gain)
- …. exothermic (loss

Question 4

what does delta H mean?

Answer 4

change in enthalpy

Question 5

what is delta S

Answer 5

change in entropy

Question 6

enthalpy vs entropy?

Answer 6

Enthalpy is the amount of internal energy contained in a compound whereas entropy is the amount of intrinsic disorder within the compound. Enthalpy is zero for elemental compounds such hydrogen gas and oxygen gas; therefore, enthalpy is nonzero for water (regardless of phase).

Question 7

equation for delta G using temperature, enthalpy and entropy

Answer 7

Question 8

Answer 8

write combustion of methane formula
1. Ch4+02–>CO2 +2H20

use Hess’s law to calculate the enthalpy of reaction
2. delta H = sum of products enthalpy - sum of reactants enthalpy
3. the right side shows each compound being evaluated. sum each of their enthalpies

Question 9

elements in standard states like O2(g) have an enthalpy of __

Answer 9

0

Question 10

what kind of heat transfer is used in microwaves?

Answer 10

(electromagnetic) radiation

(which includes visible and UV light, X ray, gamma rays, IR, radio waves which travel without a medium

Question 11

convection vs conduction

Answer 11

conduction: direct conract
convection: through bulk motion of fluids

Question 12

what will increase rate of forward reaction?

Answer 12

• adding reactant
• increasing temperature (endothermic –> increaseing temp increases forward rate)
• removing product

not incr/dec pressure when moles of gas are equal on both sides

Question 13

what is the expression for the equilibrium constant for the dissolution of silver sulfate (Ag2SO4) in water?

Answer 13

equal to concentration of products over reactants

do not include any solids or pure liquids, only aq

1. equation
2. Ag2SO4 (s) –> 2 Ag+ (aq) + SO42- (aq)

since Ag2SO4 is a solid, EXCLUDE

3. take the stiochiometric coefficient and make it the exponent for that component in the expression

2 AG+ becomes [Ag]^2

4. put it together
   [Ag+]^2[SO4 2-]

Question 14

which would support role of solid platinum as a catalyst in the conversion of Carbon monoxide into carbon dioxide?

• overall mass of platinum does not change during reaction
• solid block of platinum increase rate of reaction more than finely ground platinum
• rate of carbon dioxide formation is increased in presence of platinum
• rate of carbon monoxide depletion is increased in presence of platinum

Answer 14

will support catalyst

• overall mass of platinum does not change during reaction
• rate of carbon dioxide formation is increased in presence of platinum
• rate of carbon monoxide depletion is increased in presence of platinum

does not
- solid block of platinum increase rate of reaction more than finely ground platinum

grounding would increase surface area, and actually make it better than solid