It is estimated that the Coma Cluster contains about 10^13 Mass of the Sun of intracluster gas. Assuming that this gas is made of hydrogen atoms, calculate the total number of intracluster gas atoms in the Coma Cluster
Look up the mass of the Sun and the mass of a hydrogen atom. (google it). Divide the mass of the Sun by the mass of a hydrogen atom to find out how many hydrogen atoms it takes to have the same mass as the Sun. Make sure you get the units the same for both. That means if the mass of the Sun is in kilograms that you need the mass of the hydrogen in kilograms too. The mass of the atom will be a very small fraction of a kilogram and the mass of the sun will be a large number of kilograms. When you divide a large number by any number less than 1, the answer is an even larger number. Then multiply by 10^13.
Add up the mass of the proton and electron of the hydrogen atom. Use that sum as a divisor/numerator to divide into the mass of the sun times 10^13 to find the number in hydrogen atoms. be sure that your units of mass are consistent, like kilograms, or you'll get the exponent incorrect. Double and triple check your calculations until you get the same answer every time. I'm ignoring that some of those hydrogen items will be deuterium and tritium atoms.
