Answer:- 
Explanations:- Alkanes are non polar molecules as these only have carbons and hydrogens. Electron negativity difference of C and H is very low and it makes them non polar. These have weaker London dispersion forces.
The forces of attraction becomes stronger in alkanes as the number of carbon increases because the surface area as well as molecular weight of the alkanes increases with an increase in number of carbons.
Butane has four carbons, propane has three carbons, ethane has two and methane has only one carbon, So, the strongest to weakest order of inter molecular forces is butane > propane > ethane > methane .
1 mole = 6.22 x 10^23 molecules (Avogadro's number)
15 moles x (6.22 x 10^23) = 9.33 x 10^24 atoms
Answer: B is the answer i believe.
Recycling!! And also planting more trees.
Hope this helps!
One: looks to be correct for both answers. Certainly the first one is. The second depends on your other choices. But military use is one.
Two: is correct. Pd has (in this case) an atomic mass of 114 and its number is 46
Three: Even with my slop numbers, 4.98 is the answer (although I get 4.99 but again, my numbers are pretty sloppy).
Four: Slop numbers say 78.3, but 78 is the right answer.
Five: Slop numbers agree with Al2S3. I think that's D
They are all correct. Very Fine Work.
