Answer: The expression for equilibrium constant is ![\frac{[NH_3]^2}{[H_2]^3[N_2]}](https://tex.z-dn.net/?f=%5Cfrac%7B%5BNH_3%5D%5E2%7D%7B%5BH_2%5D%5E3%5BN_2%5D%7D)
Explanation: Equilibrium constant is the expression which relates the concentration of products and reactants preset at equilibrium at constant temperature. It is represented as 
For a general reaction:

The equilibrium constant is written as:
![k_c=\frac{[C]^c[D]^d}{[A]^a[B]^b}](https://tex.z-dn.net/?f=k_c%3D%5Cfrac%7B%5BC%5D%5Ec%5BD%5D%5Ed%7D%7B%5BA%5D%5Ea%5BB%5D%5Eb%7D)
Chemical reaction for the formation of ammonia is:


Expression for
is:
![k_c=\frac{[NH_3]^2}{[H_2]^3[N_2]}](https://tex.z-dn.net/?f=k_c%3D%5Cfrac%7B%5BNH_3%5D%5E2%7D%7B%5BH_2%5D%5E3%5BN_2%5D%7D)
![1.6\times 10^2=\frac{[NH_3]^2}{[H_2]^3[N_2]}](https://tex.z-dn.net/?f=1.6%5Ctimes%2010%5E2%3D%5Cfrac%7B%5BNH_3%5D%5E2%7D%7B%5BH_2%5D%5E3%5BN_2%5D%7D)

<h3>Further explanation</h3>
Given
3000 L of gas at 39°C and 99 kPa to 45.5 kPa and 16°C,
Required
the new volume
Solution
Combined with Boyle's law and Gay Lussac's law

T₁ = 39 + 273 = 312
T₂ = 16 + 273 = 289
Input the value :
V₂ = (P₁V₁.T₂)/(P₂.T₁)
V₂ = (99 x 3000 x 289)/(45.5 x 312)
or we can write it as:
V₂ = 3000 L x (289/312) x (99/45.5)
<h3>Balanced equation :
2C₂H₆ (g) + 7O₂ (g) ⟶ 4CO₂ (g) + 6H₂O (ℓ)</h3><h3>Further explanation</h3>
Alkanes are saturated hydrocarbons that have single bonds in chains
General formula for alkanes :

Hydrocarbon combustion reactions (specifically alkanes)

So that the burning of ethane with air (oxygen):

2C₂H₆ (g) + 7O₂ (g) ⟶ 4CO₂ (g) + 6H₂O (ℓ)
or we can use mathematical equations to solve equilibrium chemical equations by giving the coefficients for each compound involved in the reaction
C₂H₆ (g) + aO₂ (g) ⟶ bCO₂ (g) + cH₂O (ℓ)
C : left 2, right b ⇒ b=2
H: left 6, right 2c⇒ 2c=6⇒ c= 3
O : left 2a, right 2b+c⇒ 2a=2b+c⇒2a=2.2+3⇒2a=7⇒a=7/2