Suppose that you massed out 3.50 g of sodium carbonate, Na2CO3. How many moles would you have?

0.0330 moles Na2CO3

Explanation: You divide 3.50 grams by the molar mass of Na2CO3, which is 105.99 g/mol. The grams will cancel out and you're left with 0.0330 moles NA2CO3. The answer will have 3 sig figs.

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."