Answer:
A) Sample B has more calcium carbonate molecules
Explanation:
M = Molar mass of calcium carbonate = 100.0869 g/mol
= Avogadro's number = 
For the 4.12 g sample
Moles of a substance is given by

Number of molecules is given by

For the 19.37 g sample

Number of molecules is given by


So, sample B has more calcium carbonate molecules.
The ratio of the elements of carbon, oxygen, calcium atoms, ions, has to be same in both the samples otherwise the samples cannot be considered as calcium carbonate. Same is applicable for impurities. If there are impurites then the sample cannot be considered as calcium carbonate.
Nitrous Acid.
Hyponitrous acid: H2N2O2
Nitric acid: HNO3
Pernitric acid: HNO
There can only be two electrons in the innermost shell of an atom so b is the correct answer
Answer:
The answer to your question is below
Explanation:
1. Found in period 2. All the elements in the list are found in period 2.
a. F This option is correct
b. Be Beryllium is located in period two.
c. O also oxygen is found in period 2.
d. C Carbon is found in period 2.
2.- Can gain lose 4 electrons to become its nearest stable noble gas. Only Carbon.
a. F This option is wrong, F becomes stable when it gains 1 electron.
b. Be Beryllium becomes stable when it loses 2 electrons.
c. O Become stable when it gains 2 electrons.
<u>d. C </u><u>Become stable when it gains or loses 4 electrons.</u>