Because in CH4 the valence electrons of Carbon are being pulled away from the nucleus with the same force (since all hydrogen has the same electronegativity).So charges are equally distributed throughout the atom and the atom is non-polar. In CH3Cl Cl has a different electronegativity than H, so charges aren't equally distributed and therefore the molecule is polar.
# of atoms per mol = Avogadro’s # (6.022 x 10^23)
Number of mols = mass of substance / molar mass
73 g / 40.08 g = 1.8 mols of Ca in 73 grams
1.8 mols x avagadro’s # = 1.1 x 10^24 atoms in 73 grams of Ca
A water solution is found to have a molar oh- concentration of 3.2 x 10-5. the solution would be classified as neutral.
The concentration of hydroxide ions (OH-) is measured by pOH. It is a way of expressing how alkaline a solution is. At 25 degrees Celsius, aqueous solutions with pOH values of 7 or less are neutral, whereas those with pOH values of 7 or more are acidic. The hydrogen ion potential is known as pH. The potential of hydroxide ions is known as pOH. 2. It is a scale used to estimate the hydrogen ion (H+) concentration in the solution. The hydroxide ion (OH-) concentration of the solution is measured using this scale.
pH + pOH = 14
pOH = 3.2x 10-5
[OH-] = 10^(-pOH) =10^(- 3.2x 10-5)
= 0.99
Volume perhaps ?
Hope this helps !