The answer is 1 and 3. The number of atoms per molecule of these three substance is not equal. So they will not contain same number of atoms. And for gas, under same condition with same number of moles will have the same volume. The g.f.w is related to the atomic mass. So they are different.
Answer: You multiply and divide when rounding division significant figures
Explanation: Both multiplying and dividing significant figures have the same rule. That rule is, the FINAL ANSWER of a multiplication and division problem should be rounded to the number of significant figures that is the least amount of any figures used in the multiplication or division. Let us demonstrate below.
The answers are: T, T, F, T, T, T