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 is: because they were using simple chemical reactions to transform elements, but that is possible only with nuclear reactions, which in that time were not possible to conduct.
Nuclear reactions can produce new elements, because number of protons and neutrons is changed, lead and gold have different atomic and mass numbers.
The electrons of an atom participates in a chemical reaction, chemical reactions involve the rearrangement of electrons, because there is transfer, loss, gain and sharing of electrons in chemical reactions, new elements are not formed.
Answer:
3.46x10⁴
Explanation:
Hello,
In this case, we can see that the number 34,560 has five significant figures, it means that if we want to write it with three, we must take the 3, 4 and 5 only. Nevertheless, since the 6 after the five is greater than 5, we can round such five to 6, so we obtain:
346
However, the decimal places cannot get lost, therefore, we move the given thousand to the three, so the number turns out:
3.46x10⁴
Best regards.
Number of proton K=19
so, 42 - 19 =23
then the answer in 19 protons and 23 neutrons
Which statement describes how the binary ionic compound KBr is named? The metal is named first, and the name is unchanged. Which of these is a property of a substance that is composed of atoms that are held together by ionic bonds?
