A 0.674\,\text M0.674M0, point, 674, start text, M, end text cobalt(II) chloride (\text{CoCl}_2CoCl 2 start text, C, o, C, l, end text, start subscript, 2, end subscript) solution is prepared with a total volume of 0.0750\,\text{L}0.0750L0, point, 0750, start text, L, end text. The molecular weight of \text{CoCl}_2CoCl 2 start text, C, o, C, l, end text, start subscript, 2, end subscript is 128.9\,\dfrac{\text{g}}{\text{mol}} 128.9 mol g 128, point, 9, start fraction, start text, g, end text, divided by, start text, m, o, l, end text, end fraction.

The mass of this CoCl2 sample is 6.516 grams

Explanation:

Step 1: Data given

Molarity of a cobalt(II) chloride (CoCl2) solution is 0.674 M

Volume of the solution is 0.0750 L

The molecular weight of CoCl2 is 128.9 g/mol

Step 2: Calculate moles CoCl2

Moles CoCl2 = molarity CoCl2 solution * volume solution

Moles CoCl2 = 0.674 M * 0.0750 L

Moles CoCl2 = 0.05055 moles

Step 3: Calculate mass of the CoCl2 sample

Mass CoCl2 = moles CoCl2 * molar mass CoCl2

Mass CoCl2 = 0.05055 moles * 128.9 g/mol

Mass CoCl2 = 6.516 grams

The mass of this CoCl2 sample is 6.516 grams

"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."

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