chem
posted by alex on .
Now the numbers in the question are correct, (Fluorine = 10.10atm Krypton = 1.24atm). Please help.
Fluorine and krypton react to form binary compounds when a mixture of the two gases is heated to 500C in a nickel reaction vessel. A 100mL nickel container is filled with fluorin and krypton to partial pressures of 10.10 atm and 1.24 atm, respectively at a room temperature of 20 C. The reaction vessel is heated to 500 C and then cooled to a temperature at which F2 is a gas and krypton fluorides are nonvolatile solids. The remaining F2 gas is transferred to another 100mL nickel container where the pressure of F2 at 20C is 7.2 atm. Assuming all the krypton has reacted, what is the formula of the product?

Use PV = nRT and solve for n for number moles F2 initially.
Use PV = nRT to solve for n for Kr initially.
Use PV = nRT to solve for moles F2 after the reaction.
All of the moles Kr reacted.
moles F2 reacted = moles initially  moles at the end.
So now you have n Kr = about 0.005
n F2 = about 0.012
Take the ratio of the two numbers to make whole numbers with the smaller one being 1.00. The easy way to do that is to divide the 0.005 by itself (it isn't exactly 0.005) and divide the other number by the same small number. I think you will get something like 1.00 for Kr and 2.33 for F2. Convert that to whole numbers. The easy way is to multiply both by 1, then 2, then 3, then 4, etc until you come up with a number very close to whole numbers, then round to the appropriate whole numbers. For example, multiplying by 2 will give you 2.00 to 4.66. Multiplying by 4 will give you 4.00 to 8.32 so it isn't KrF2.33 or Kr2F4.66 or Kr4F8.32 but you might try multiplying by 3.