If you start with the mass of a substance, divide it by its molar mass to find the number of moles of the substance. Then, multiply the number of moles by Avogadro's number, 6.022*10^23, which gives the number of particles per mole of a substance.
Example:
Find the number of atoms in 10 g of CO2.
The mass of a single mole of CO2 is 54 g/mol. You can get this value by adding up the molar masses of the atoms in CO2(12+16+16).
Then divide 10 g by 54 g/mol to get the number of moles of CO2 in 10 g, which is 0.19 mol.
Finally, multiply 0.19 by Avogadro's number to get 1.1*10^23 molecules of CO2.
Answer:
Density = 1.56 g/mL
Explanation:
We have two sort of concentrations in here, so let's combine them.
% by mass means grams of solute in 100 g of solution
M means, moles of solute in 1L of solution.
We know that our solute is KOH (Molar mass = 56.1 g/mol)
We convert the moles of solute to grams:
56.1 g/mol . 13.9 moles = 779.79 g
Now, we know that 50 g of solute are in 100 g of solution
Then, 779.79 g of solute will be contained in (100 . 779.79)/50 = 1559.58 g of solution
Density = mass / volume
1559.58 g of solution / 1000 mL of solution = 1.56 g/mL
I think it is C but I'm not sure.
