Ammonium carbamate (nh2coonh4) is a salt of carbamic acid that is found in the blood and urine of mammals. at 202°c, kc = 0.008 for the following equilibrium: if 6.82 g of nh2coonh4 is put into a 0.5-l evacuated container, what is the total pressure (in atm) at equilibrium? enter a number to 2 decimal places.

P(total) = 46.08 atm

Explanation:

Given data:

Mass of NH₂COONH₄ = 6.8 g

Kc = 0.008

Temperature = 202°C = 202+273 = 475 K

Total pressure at equilibrium = ?

Solution:

Equilibrium equation:

NH₂COONH₄   ⇄   2NH₃ + CO₂

Formula:

Kp = Kc(RT)³

Kp = 0.008 (0.0821 atm.L/mol.K )³(475K)³

Kp = 471.56

                                                                  NH₃       CO₂

            Initial concentration                       0          0

            Change in concentration             2x           x

            equilibrium concentration            2x           x

AS

471.56 = 2x (x)

471.56 = 2x²

x² = 471.56 /2

x² = 235.78

x = 15.36

Pressure of ammonia = 2x = 2(15.36) = 30.72 atm

Pressure of carbon dioxide = x = 15.36 atm

Total pressure:

P(total) = P(NH₃) + P(CO₂)

P(total) = 30.72 atm +  15.36 atm

P(total) = 46.08 atm

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