Combining Equilibrium Constants.

It is possible to predict the equilibrium constant of a reaction by combining two or more reactions for which the value of K is known. When combining equilibrium constants, it is important to note the following:

When a reaction is reversed, its Kvalue is inverted; that is, Kreverse=1/Kforward.

When the coefficients of a reaction are multiplied by a factor, the Kvalue is raised to the power of that factor.

When reactions are added, their Kvalues are multiplied.

Part A

Determine the value of the equilibrium constant, Kgoal, for the reaction

N2(g)+H2O(g)⇌NO(g)+12N2H4(g), Kgoal=?

by making use of the following information:

1. N2(g)+O2(g)⇌2NO(g), K1 = 4.10×10−31
2. N2(g)+2H2(g)⇌N2H4(g), K2 = 7.40×10−26
3. 2H2O(g)⇌2H2(g)+O2(g), K3 = 1.06×10−10
Part B

Determine the equilibrium constant, Kgoal, for the reaction

4PCl5(g)⇌P4(s)+10Cl2(g), Kgoal=?

by making use of the following information:

P4(s)+6Cl2(g)⇌4PCl3(g), K1=2.00×1019

PCl5(g)⇌PCl3(g)+Cl2(g), K2=1.13×10−2

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.

plasma - state of matter made up of electrically charged particles