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.
C......…..……...............
Answer:
-37.63KJ
Explanation:
First, we write an equation of reaction:
H + Br ——-> HBr
Now we are told that 155g of HBr is formed. We can calculate the number of moles of HBr formed as follows:
We simply divide the mass of the HBr formed by the molar mass of HBr. The molar mass of HBr is 81g/mol
The number of moles of HBr formed is thus 81/155 = 0.52 moles
The amount of heat released is thus 0.52 * (-72) = -37.63KJ
Answer:
D
Explanation:
Acceleration = velocity/time
A = 2*20
A = 0.10 m/s²
Answer:
D. CF₄
Explanation:
The compound with this molecular geometry is Carbon tetrafluoride (CF₄)
Carbon tetrafluoride (CF₄) also known as Tetrafluoromethane, is known to be the simplest perfluorocarbon. The compound, tetrafluoromethane is the hydrocarbon methane has been perfluorinated. It useful as a refrigerant but known to be a greenhouse gas. Due to the nature of the carbon-flourine bond, it has very high bonding strength. Its bonds are known to be the strongest single bonds in organic chemistry.
Option D is the correct answer.
