Answer:
pH =3.8
Explanation:
Lets call the monoprotic weak acid HA, the dissociation equilibria in water will be:
HA + H₂O ⇄ H₃O⁺ + A⁻ with Ka = [ H₃O⁺] x [A⁻]/ [HA]
The pH is the negative log of the H₃O⁺ concentration, we know the equilibrium constant, Ka and the original acid concentration. So we will need to find the [H₃O⁺] to solve this question.
In order to do that lets set up the ICE table helper which accounts for the species at equilibrium:
HA H₃O⁺ A⁻
Initial, M 0.40 0 0
Change , M -x +x +x
Equilibrium, M 0.40 - x x x
Lets express these concentrations in terms of the equilibrium constant:
Ka = x² / (0.40 - x )
Now the equilibrium constant is so small ( very little dissociation of HA ) that is safe to approximate 0.40 - x to 0.40,
7.3 x 10⁻⁶ = x² / 0.40 ⇒ x = √( 7.3 x 10⁻⁶ x 0.40 ) = 1.71 x 10⁻³
[H₃O⁺] = 1.71 x 10⁻³
Indeed 1.71 x 10⁻³ is small compared to 0.40 (0.4 %). To be a good approximation our value should be less or equal to 5 %.
pH = - log ( 1.71 x 10⁻³ ) = 3.8
Note: when the aprroximation is greater than 5 % we will need to solve the resulting quadratic equation.
<u>Answer:</u>
The correct answer option is B) 2.0 M.
<u>Explanation:</u>
We are given the number of grams of NaOH (Sodium Chloride) which are dissolved in 750 milliliters of water and we are to find its molarity.
We know the formula of molarity:
<em>Molarity = (mass * 1000) / (volume * molecular mass) </em>
Volume = 750 ml = 750 cm
Molecular mass = 40
Mass = 60 grams
Substituting these values in the above formula:
Molarity = 
= 2.0 M
Answer:
Idk if this is right but i hope it helps... sorry if it's wrong
Explanation:
All matter is made up of particles called atoms and molecules (as opposed to being continuous or just including particles). On the following page, the idea is stated as one of four concepts in Dalton's theory: “All matter is composed of tiny, indivisible particles called atoms” (p. 158s).
