Answer:
1) Molar mass of NaOH can be calculated by taking the atomic mass values in the periodic table. Na (Sodium) = 22.98g/mol, O (Oxygen) = 16g/mol, H (Hydrogen) = 1.01g/mol
Add all the the mass values together for NaOH's molar mass, so (22.98 + 16 + 1.01) = 39.99 or round it to 40g/mol
2) To find the atoms from the moles, you just multiply Avogadro's number (6.02 x 10^23) by the moles.
So 3.35 x (6.02 x 10^23) = 2.0167 x 10^24 atoms are in 3.35 moles of aluminum
3) If the question is asking under standard temperature and pressure, we know that if we divide the volume by the molar volume of a gas (which is 22.7 in standard temperature and pressure), we can get the moles.
So 101.25L / 22.7 = 4.46 mol
4) We know that to find the moles, it is the mass divided by the molar mass. If we rearrange the equation to solve for mass, we have to multiply the moles by the molar mass to get there.
Nitrogen's (N) molar mass on the periodic table is 14g/mol, but since Nitrogen is a diatomic element, it would be N2 by itself. So multiply 14 by 2, which will give you 28g/mol. N2's molar mass is 28g/mol.
Now you multiply 13.7 moles by 28g/mol, which will give you 383.6g
5) Now here I think you may have wrote the question wrong. Molecules would be at a way higher number than just 78.5, so I'm first just going to assume you meant 78.5g.
To get the moles from mass, you divide the mass of the compound by its molar mass. Molar mass of CaCO3 can be just calculated using the atomic mass values for each element in the compound (Ca is 40.07g/mol, C is 14g/mol, O3 would be 16 x 3 g/mol or just 48g/mol) and then adding them all together (40.07 + 14 + 48 = 102.07) which would give us 102.7g/mol.
Now, just divide the mass 78.5g by the molar mass 102.7g/mol
78.5/102.7 = 0.764 moles
Now on the offchance that you were actually referring to molecules, and you accidentally typed a different number doing this, you can find out the moles from the molecules by just dividing the number of molecules you have with avogadro's number (6.02 x 10^23)
So it would look something like this:
molecules of CaCO3 / 6.02 x 10^23
