To determine the diffusion coefficient D of a gas using Graham's law of diffusion, we need to know the rate of diffusion r , the molecular weight M of the gas, and the temperature T and pressure P of the system. Graham's law states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight.First, let's write down the formula for Graham's law:r1 / r2 = M2 / M1 where r1 and r2 are the rates of diffusion of two different gases, and M1 and M2 are their respective molecular weights. In this case, we only have one gas, so we can simplify the formula as follows:r = k * 1 / M where k is a proportionality constant.Now, we need to find the diffusion coefficient D . The diffusion coefficient is related to the rate of diffusion r by the following equation:r = D * C / x where C is the concentration difference between two points and x is the distance between those points.We can rearrange this equation to solve for D:D = r * x / C Now, we can substitute the expression for r from Graham's law into this equation:D = k * 1 / M * x / C To find the value of k, we can use the known values of temperature T and pressure P . The proportionality constant k can be expressed as:k = RT / P * 2 where R is the universal gas constant 8.314 J/molK .Now, we can substitute the expression for k into the equation for D:D = RT / P * 2 * 1 / M * x / C Finally, the student can plug in the known values for R, T, P, M, x, and C to calculate the diffusion coefficient D of the gas.