Question

The color of $CuC{r_2}{O_7}$ solution in water is green because.
a.) $C{u^{2 + }}$ ion is green.
b.) $C{r_2}O_{_7}^{2 - }$
c.) Both the ions are green
d.) $C{u^{2 + }}$ ion is blue and $C{r_2}O_{_7}^{2 - }$ ion is yellow

Answer 1

Hint: This question gives the knowledge about the colors of chemical species. The color of chemical compounds are based on the process of excitation of electrons when absorption of energy takes place.

Complete step by step answer:
copper consists of unpaired electrons which can act as F centre and generally allows transition of electrons in the visible region which imparts color. $C{u^{2 + }}$ ions are green in color and the $C{r_2}O_{_7}^{2 - }$ ions are yellow in color. When these both colors mix with each other results in the formation of a green color solution of $CuC{r_2}{O_7}$.
The correct option is option “4” .

Additional Information .
- The color of chemical compounds are based on the process of excitation of electrons when absorption of energy takes place. Color of chemical species is a physical property which can be acknowledged through naked eyes. The color that we see through our eyes is not the color that is absorbed, but is actually the complementary color from the elimination of the absorbed wavelengths.
- Complementary colors are defined as the pairs of colors which on combining or mixing with each other cancels out each other’s hue to produce grayscale color. Complementary colors are also known as opposite colors. The pairs of complementary colors are red and green, yellow and purple, blue and orange, red-orange and blue-green and so forth. This shows that when red color is absorbed it emits out green color.

Note: Always remember that the color of chemical species is a physical property which can be acknowledged through naked eyes. Complementary colors are also known as opposite colors because one color is absorbed and the other color is emitted out.