What is the wavelength (in nm) of a quantum of light that has an energy of 4.97 X 10-19 J? What color is it?

The answer is right in front of you!
E = hv (v being nu = frequency)
lv = c (l being lambda = wavelength, c = speed of light)
l = c/v
v = E/h
therefore l = ch/E just plug in the three numbers! then you can refer to your textbook for the color.

Try this.
4.97 X 10^-19J = ( 6.626 X 10^-34)(2.998 X 10^8)/ X
4.97 X 10^-19X = 1.98 X 10^-25
X = 3.99 X 10^-7 meters X 10^9
= 399 nanometers
I do not have a chart to hand, but this should be in your book for the color.

if you know how to do it, why don’t you do it.
E=hν
4.97×10ˉ¹⁹J÷6.626×10ˉ³⁴Js=
750,075,460,307,878s
2.99792458 × 10¹⁷ nanometers / second ÷ 750,075,460,307,878s = 399.683 nm
that’s violet