Nitric acid and nitrogen monoxide react to form nitrogen dioxide and water, like this: (aq)(g)(g)(l) At a certain temperature, a chemist finds that a reaction vessel containing a mixture of nitric acid, nitrogen monoxide, nitrogen dioxide, and water at equilibrium has the following composition: compoundamount Calculate the value of the equilibrium constant for this reaction. Round your answer to significant digits.

The reaction given is  

Chemistry homework question answer, step 1, image 1

Since in equilibrium constant expression, the concentration of liquid components is not written.

Hence the equilibrium constant expression for the above reaction can be written as  

Chemistry homework question answer, step 1, image 2

where [NO] = equilibrium concentration of NO

[NO2 ] = equilibrium concentration of NO2

[HNO3 ] = equilibrium concentration of HNO3

Step 2

Given : mass of NO at equilibrium = 18.6 g

mass of NO2 at equilibrium = 15.1 g

and mass of HNO3 at equilibrium = 13.1 g

Since molar mass of HNO3 = 63 g/mol, molar mass of NO = 30 g/mol and molar mass of NO2 = 46 g/mol

Hence the moles of gases at equilibrium are

Chemistry homework question answer, step 2, image 1

Step 3

Since mass of solution = mass of HNO3 + mass of water = 13.1 + 234.8 = 247.9 g

Assuming density of solution = density of water = 1.00 g/mL

=> mass of solution = volume of solution X density of solution  

=> 247.9 = 1.00 X volume of solution  

=> volume of solution = 247.9 mL = 0.2479 L      

Explanation:

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.