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.
The answer should be; 11
The atomic mass number is found by combining the number of protons and neutrons
Hope this helps :)
Record observations, pose a question, create a test for an individual variable, test, come to a conclusion
86 elections so 43 orbitals
Answer:
Nucleus
Explanation: it is the center of the atom, and contains protons and nuetrons