Answer:
0.10 % w/w
Explanation:
The percent by mass (%w/w) is defined as one hundred times the ratio between the mass of solute (In this case aspirin, 0.05g) and the mass of solution (Mass solute + mass of water = 0.05g + 50g = 50.05g). The percent by mass is:
0.05g Aspirin / 50.05g * 100 =
0.10 % w/w
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:
26.110 grams of O2 produced.
Explanation:
Calculate the amount of moles in KClO3 by dividing the amount of grams given by the atomic weight of the substance.
To get the atomic weight: K = 39.098, Cl = 35.45, O = 15.999, and there are 3 molecules of Oxygen, so multiply 15.999 by three.
39.098 + 35.45 + (15.999 * 3) = 122.548.
66.7g / 122.548 atomic mass = 0.544 moles.
The ratio of moles of KClO3 to moles of O2 is 2 to 3.
= 
Cross multiply to get 1.632 = 2y. Y = 0.816, meaning 0.816 moles of O2 will be produced.
Convert this into grams by multiplying by the atomic weight of O2 (15.999 * 2 = 31.998).
0.816 * 31.998 = 26.110 grams of O2 produced.
Answer:
its endothermic .
because your using a cooling process instead of a heating process if it was a heating process it would be exothermic
