# Ratio of rate of diffusion of two gases under constant temperature and pressure

I'm consulting one of higher classes books to study chemistry. I had been studying Graham's Law and question related to rate of diffusion. I came across a question[1] which says:

Calculate the ratio of diffusion of $$\ce{SO2}$$ and $$\ce{CO2}$$ under constant temperature and pressure.

The question mentioned the mass of elements as following: $$\ce{S}=32$$, $$\ce{O}=16$$, $$\ce{C}=12$$.

My solution of the question:

Molecular mass of $$\ce{SO2}=32+32=64$$

Molecular mass of $$\ce{CO2}=12+32=44$$

$$\frac{\textrm{Rate of diff. of}\ \ce{SO2}}{\textrm{Rate of diff. of}\ \ce{CO2}} = \sqrt{\frac{44}{64}} = \frac{\sqrt{11}}{4}$$

But the book has a different answer at the back, where it says $$1:2$$. I rechecked and performed all the maths again, but still cannot find this answer. Is the book incorrect, or have I made a mistake? If the latter, please help me find it.

1. D. N. Singh: Basic Concepts of Inorganic Chemistry, 2nd Edition. Pearson India, December 2011. ISBN: 9788131768617 URL of publisher
• If you made a mistake, I'm making the same. To me, your solution looks fine! – Klaus-Dieter Warzecha Apr 20 '15 at 7:56
• I think you're right here as well... – Asydot May 1 '15 at 14:53