Question

Which of the following is an example of the law of multiple proportions?

		two different samples of table salt are found to have the same ratio sodium to chlorine
		carbon dioxide always has the same mass ratio
		a sample of chlorine is found to contain three times as mush 35Cl as 37Cl.
		two different compounds formed from nitrogen and oxygen have the following mass ratio: 1g N: 2.28 g O and 2g N : 2.28 g O

Answer 1

Law of multiple proportions states that a given compound formed out of two or more than two elements will always have its elements combining in a fixed ratio by weight.

Let's take CO₂ as an example

Carbon has a mass of 12 g and oxygen has a mass of 32 g in a mole of CO₂ sample.

Now, you can bring any sample from anywhere having any amount of CO₂ but every sample will have Carbon/Oxygen ratio of 12/32 or 1/2.66

Coming to the question

(A)

Option A very nicely explains that in any two different samples of table salt, which is NaCl, we always get a fixed sodium/chlorine ratio.

(B)

Option B doesn't clearly say as to which mass it is pointing.

(C)

Option C is actually the limitation of law of multiple proportion. For example in a table salt which has chlorine, you can also sometimes get an isotope of chlorine which has a mass of 37amu. The isotope of Chlorine is rare though.

(D)

Option D talks about the masses of nitrogen and oxygen combining in a given ratio but it doesn't state anything about those ratio being fixed.

Therefore Option A seems to be appropriate.