0.45g sample of mineral ore is analyzed for chromium and found contain 0.560mg Cr2 O3. Express concentration of Cr2O3 in sample as percent

0.124% of Cr2O3 in the sample

Explanation:

A mass percent is expressed as 100 times the ratio of the mass of analyte and the mass of the sample. For this problem, the equation is:

Mass Cr2O3(g) / Mass Mineral(g) * 100

To solve this question we must convert the mass of Cr2O3 to grams and then, compute the value in the equation:

Mass Cr2O3 in g:

0.560mg * (1g / 1000mg) = 5.6x10⁻⁴g Cr2O3

Percent of Cr2O3 is:

5.6x10⁻⁴g Cr2O3 / 0.45g * 100

"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."