Best Answer
C) is the best description, although a scientific theory is not necessarily a "fact". They are, however, based on evidence.
A) is complete garbage.
B) is a good description of a scientific "law"- something that predicts how a certain event will occur without explaining why this is (for instance, the law of gravity accurately describes the gravitational forces between two bodies, but does not explain why these forces are there).
D) is a scientific "hypothesis"- an explanation for an observed phenomena that is yet to be proven.
The concentration of [H3O⁺]=2.86 x 10⁻⁶ M
<h3>Further explanation</h3>
In general, the weak acid ionization reaction
HA (aq) ---> H⁺ (aq) + A⁻ (aq)
Ka's value
![\large {\boxed {\bold {Ka \: = \: \frac {[H ^ +] [A ^ -]} {[HA]}}}}](https://tex.z-dn.net/?f=%5Clarge%20%7B%5Cboxed%20%7B%5Cbold%20%7BKa%20%5C%3A%20%3D%20%5C%3A%20%5Cfrac%20%7B%5BH%20%5E%20%2B%5D%20%5BA%20%5E%20-%5D%7D%20%7B%5BHA%5D%7D%7D%7D%7D)
Reaction
HC₂H₃O₂ (aq) + H₂O (l) ⇔ (aq) + H₃O⁺ (aq) Ka = 1.8 x 10⁻⁵
![\tt Ka=\dfrac{[C_2H_3O^{2-}[H_3O^+]]}{[HC_2H_3O_2]}}\\\\1.8\times 10^{-5}=\dfrac{0.22\times [H_3O^+]}{0.035}](https://tex.z-dn.net/?f=%5Ctt%20Ka%3D%5Cdfrac%7B%5BC_2H_3O%5E%7B2-%7D%5BH_3O%5E%2B%5D%5D%7D%7B%5BHC_2H_3O_2%5D%7D%7D%5C%5C%5C%5C1.8%5Ctimes%2010%5E%7B-5%7D%3D%5Cdfrac%7B0.22%5Ctimes%20%5BH_3O%5E%2B%5D%7D%7B0.035%7D)
[H₃O⁺]=2.86 x 10⁻⁶ M
Answer:
The element will be 
Explanation:
Given that,
Number of proton = 80
Number of neutron = 81
Number of electron = 79
We know that,
The atomic number is equal to the number of proton.
So, the atomic number is 80.
According to atomic number,
The element will be mercury.
We need to calculate the atomic mass
Using formula of atomic mass

Put the value into the formula


We need to find the element
Using atomic mass and atomic number


So, the element will be

Put the value of A and Z
Hence, The element will be 