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.
<h3>
Answer:</h3>
Distance = 7 m
Power = 12.5 J/s or watts
<h3>
Explanation:</h3>
Work done = 175 Joules
Force exerted = 25 Newtons
Work done is the product of force exerted and the distance moved by a body.
Therefore;
Work done = Force × distance
Rearranging the formula we can work out the distance;
Distance = work done ÷ Force
= 175 J ÷ 25 N
= 7 m
Thus, the grand piano was moved by 7 m across the living room .
On the other hand,
Power is the rate at which the work is done.
Therefore;
Power = Work done ÷ time
Work done = 175 Joules
Time = 14 seconds
Thus;
Power generated = 175 J ÷ 14 sec
= 12.5 J/s or watts
Hence, a power of 12.5 J/s was generated in moving the grand piano.
Answer:
The experiment that did not give the results described is e) The Rutherford experiment proved the Thomson "plum-pudding" model of the atom to be essentially correct.
Explanation:
- First of all, let's start with the experiment listed in <em>b) The Rutherford experiment was useful in determining the nuclear charge on the atom</em>. This is true, because Rutherford was able to tell through this experiment that the atoms consisted mostly of empty space, with a positively charged nucleus in its center (he was able to tell it was positive because of the deflections observed on the positive alpha particles he used).
- Next, we have experiment <em>c) The electric discharge tube proved that electrons have a negative charge</em>. This is also true, given that Thomson was able to correctly determine that there existed particles that were negatively charged, called electrons (he determined this by observing that the rays deviated from the negatively charged plate of the discharge tube in his experiment).
- Experiment d) <em>Milikan's oil-drop experiment showed that the charge on any particle was a simple multiple of the charge on the electron</em>, also states the correct results. He was able to determine the charge of many electrically charged droplets of oil, and found out that the charges were a simple multiple of a base value, which he proposed to be that of the negative charge of an electron.
- Finally, we take a look at experiment <em>e) The Rutherford experiment proved the Thomson "plum-pudding" model of the atom to be essentially correct</em>. This is the experiment that did not give the result described. In fact, the Rutherford experiment proved that Thomson's "plum-pudding" model was not correct. This is because he determined that atoms consist mostly of empty space, with a dense, positively charged nucleus in its center, surrounded by negatively charged electrons. If Thomson's model were true, Rutherford would have not observed deflected alpha particles in his experiment.
Brakes in half maybe who really know we need help
Answer:
The number of electrons in the outermost shell of an atom determines its reactivity. Noble gases have low reactivity because they have full electron shells. Halogens are highly reactive because they readily gain an electron to fill their outermost shell.
Explanation:
