Answer: In simplest case mass of reactants is same as mass of products.
Without thinking this question deeper, mass of ZnCl2 would be 49, but..
Explanation: Reaction should be Zn + 2 HCl ⇒ ZnCl2 + H2
Amount of zinc is 5 g / 65,38 g/mol = 0,076476 mol and amount
of Hydrogen Chloride is 50 g / 36.458 g/mol = 1,371 mol.
Althought HCl is needed 0.152 moles, zinc is an limiting reactant.
So it is possible to produce only 0.076476 mol Hydrogen and its mass
is 0.154 g. Mass of ZnCl2 would be 0.076476 mol · (65.38 + 2·35.45) =
10.42 g
Answer:

Explanation:
Hello!
In this case, since we are considering an gas, which can be considered as idea, we can write the ideal gas equation in order to write it in terms of density rather than moles and volume:

Whereas MM is the molar mass of the gas. Now, since we can identify the initial and final states, we can cancel out R and MM since they remain the same:

It means we can compute the final density as shown below:

Now, we plug in to obtain:

Regards!
Thomson's model of the atom was called the plum pudding model. He discovered electrons, so he placed them in the atoms. This was before the nucleus was discovered.
Now, the current model is an atom that contains a positively charged nucleus (with both protons and neutrons), and negatively charged orbitals with electrons.
Answer:
numbers of molecules = 3×6.023×10-23