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.
Answer: 3
Explanation: I took the k12 quiz
You can start by writing out the molecular formula of each molecule.
Aluminum (Al 3+) Phosphate (PO4 3-)
AlPO4
Nickel II (Ni 2+) sulfide (S 2-)
NiS
Aluminum Sulfide
Al2S3
Nickel Phosphate
Ni3(PO4)2
If you’re wondering, we get those charges by looking at the periodic table. The metals usually have a + charge based on their group number. The nonmetals usually - charge egual to 8 - their group number.
You then balance the ions by flipping the charges, dropping the signs, and adding them in as subscripts.
Now we can put it into an equation
AlPO4 + NiS —-> Al2S3 + Ni3(PO4)2
Balance by adding coefficients
2 AlPO4 + 3 NiS —-> Al2S3 + Ni3(PO4)2
603.040 has 5 significant figures in it I'm pretty sure
Answer: Convection Currents
Explanation: The mantle rock is solid and denser because it is cooler. This means it will sink closer to lower mantle as warmer, lense dense rock/magma moves upwards.
