4 is D. 5 is C. 6 is D i guess. 7 is D.
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.
The question is missing the choices and these are CHCl3, CF4, CS2 or Br2.A polar molecule is one in which the atoms are organized such that one end of the molecule has a positive charge and the conflicting end has the opposite or negative charge. So in the given choices above, the most polar one CHCl3 this actually the only polar one in the choices. The explanation behind this is it has the same shape as CCl4 molecule, but one of the Chlorine atoms has been substituted by a Hydrogen atom. We know that Hydrogen has a weaker electronegativity in contrast to Chlorine, so electron density along the h-c bond is dragged away from the Hydrogen and in the direction of the ccl3 fragment, resulting in a polar molecule.
Answer:
Explanation:
14: Sodium Hydroxide
4: lemon juice.
10: milk of magnesia ; The great Salt Lake
7: pure water
The principal ingredient of glass is quartz sand (SiO₂).
