<span>I think the correct answer is A. A
buffer is a substance that resists small change in the acidity of a solution
when an acid or base is added to the solution. Usually, a buffer involves a
weak acid or a weak alkali and one of its salt.</span>
Awnser: C. petrolium
See, petroleum (i.e. oil) is transformed into gasoline.
"Sometimes, petroleum and crude oil are used to mean the same thing, but petroleum itself is a broad range of petroleum products including crude oil itself. We use the term 'petroleum products after crude oil is refined in a factory." - <span>www.eschooltoday.com/energy/non-renewable-energy/what-is-petroleum.html</span>
Answer:
I'm pretty sure its just the mass of the sample divided by the molar mass
for example if I had like 7g of carbon and wanted to find the moles, I would divide the mass I have (7g) by the molar mass (the atomic mass value on your periodic table, in this case for carbon it would be 14g)
moles = 
Hope this helped
