Answer:
3.24
Explanation:
The dissociation equation for the carboxylic acid can be represented as follows:
RCOOH —-> RCOO- + H+
We can use an ICE table to get the value of the concentration of the hydrogen ion. ICE stands for initial, change and equilibrium.
RCOOH RCOO- H+
Initial 0.2 0.0. 0.0
Change -x +x. +x
Equilibrium 0.2-x. x. x
We can now find the value of x as follows:
Ka = [RCOO-][H+]/[RCOOH]
(1.66* 10^-6) = (x * x)/(0.2-x)
(1.66 * 10^-6) (0.2-x) = x^2
x^2 = (3.32* 10^-7) - (1.66*10^-6)x
x^2 + (1.66 * 10^-6)x - (3.32* 10^-7) = 0
Solving the quadratic equation to get x:
x = 0.0005753650094369094 or - 0.0005753650094369094
As concentration cannot be negative, we discard the negative answer
Hence [H+] = 0.0005753650094369094
By definition, pH = -log[H+]
pH = -log(0.0005753650094369094)
pH = 3.24
The answer is D. In the visible spectrum of light, ultraviolet light has the most energy while red has the least energy. Violet light has shorter wavelengths and higher frequency. This is converse to red light that has longer wavelengths but lower frequency.
