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the equilibrium constant Kc is 0.83 at 400 C for thefollowing reaction: 2NH 3 (g

ID: 682929 • Letter: T

Question

the equilibrium constant Kc is 0.83 at 400 C for thefollowing reaction: 2NH3 (g) N2 (g) + 3H2 (g) 14.6 g of ammonia is placed in a sealed 4.00 L flask. Theflask is then heated to 400 C. calculate the concentrations of allthe gases once the system reaches equilibrium. the equilibrium constant Kc is 0.83 at 400 C for thefollowing reaction: 2NH3 (g) N2 (g) + 3H2 (g) 14.6 g of ammonia is placed in a sealed 4.00 L flask. Theflask is then heated to 400 C. calculate the concentrations of allthe gases once the system reaches equilibrium.

Explanation / Answer

Number of moles of Ammonia = 14.6 g / 17.031 g / mol                                               = 0.8572 moles Initial concentration of Ammonia = 0.8572 moles / 4.00 L                                                  = 0.2143 M                                            Kc = 0.83                                         2NH3 (g) N2 (g) + 3H2 (g)                                I(M) 0.2143          0            0                                C(M)  -2x            +x          +3x                                 E(M) 0.2143 - 2x +x          +3x                                                                                 Kc = [N2 ][H2]3 /[NH3 ]2                                              0.83    = ( x )(3x )3 /( 0.2143 - 2x)2                               ( x )(3x )3 -0.83 ( 0.2143 -2x)2   = 0 On solving above equation we get x = 0.086 M               At equilibrium :                                           [NH3]   = 0.2143 M - 2 * 0.086 M                                                        = 0.0423 M                                            [N2]     = 0.086M                                            [H2 ]    = 0.258M On solving above equation we get x = 0.086 M               At equilibrium :                                           [NH3]   = 0.2143 M - 2 * 0.086 M                                                        = 0.0423 M                                            [N2]     = 0.086M                                            [H2 ]    = 0.258M