Answer:- Frequency is
.
Solution:- The wavelength of electromagnetic radiation is given as 625 nm and we are asked to calculate the frequency. Frequency is inversely proportional to the wavelength and the formula used to calculate frequency when wavelength is given is:

where,
is frequency, c is speed of light and
is the wavelength.
Value of speed of light is
. We need to convert the given wavelength from nm to m.

So, 
= 
Let's plug in the values in the formula and calculate the frequency:

=
or Hz.
So, the frequency of the electromagnetic wave is
.
Answer:
Acids sulfuric acid, hydrochloric acid. Bases ammonia water, sodium hydroxide.
Explanation:
M = 4.79 kg = 4790 g
d = 7.86 g/cm3
density = mass/volume
v = m/d
v = 4790/7.86
v = 609.4 cm3
1 cm3 = 10^-2 dL
v = 609.4 x 0.01 = 6.09 dL
Answer:
.081 g of O2
Explanation:
4Cr + 3O2 -----> 2Cr2O3
.175 g Cr x [1 mole / 52.0 g] x [2 moles Cr2O3 / 4 moles Cr] x [152 g / 1 mole] = .256 g of Cr2O3
.175 g Cr x [1 mole / 52.0 g] x [3 moles O2 / 4 moles Cr] x [32 g / 1 mole] = .081 g of O2