Theory- <span>a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.
Scientific law- </span>a statement based on repeated experimental observations that describes some aspect of the universe.
Answer:

Explanation:
pH is derived from the concentration of hydronium ions in a solution. Hydrocyanic acid is HCN.
First, we shall figure out the moles of HCN:

If HCN was a strong acid:
HCN has a 1:1 ratio of H+ ions, the moles of H+ is also the same.
To find the molarity, we now divide by Liters. This gets us:

Finally, we plug it into the definition of pH:
![pH = -log[H^{+} ]](https://tex.z-dn.net/?f=pH%20%3D%20-log%5BH%5E%7B%2B%7D%20%5D)


However, since HCN is a weak acid, it only partially dissociates. The
of HCN is
.
![K_a = \frac{[H^+][A^-]}{[HA]}](https://tex.z-dn.net/?f=K_a%20%3D%20%5Cfrac%7B%5BH%5E%2B%5D%5BA%5E-%5D%7D%7B%5BHA%5D%7D)
We can use an ice table to determine that when x = H+,

![[H^+] = 8.83*10^{-6}](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%20%3D%208.83%2A10%5E%7B-6%7D)
![pH = -log[H^{+} ]](https://tex.z-dn.net/?f=pH%20%3D%20-log%5BH%5E%7B%2B%7D%20%5D)


The net ionic equation : Ba²⁺ + SO₄²⁻ ⇒ BaSO₄ (s)
<h3>Further explanation </h3>
The electrolyte in the solution produces ions.
The equation of a chemical reaction can be expressed in the equation of the ions
In the ion equation, there is a spectator ion that is the ion which does not react because it is present before and after the reaction
When these ions are removed, the ionic equation is called the net ionic equation
For gases and solids including water (H₂O) can be written as an ionized molecule
So only the dissolved compound is ionized ((expressed in symbol aq)
Barium sulfate can be formed from the reaction:
Ba(NO₃)₂(aq) + Na₂SO₄(aq)⇒BaSO₄(s)+2NaNO₃(aq)
For full ionic equation :
Ba²⁺ + 2NO₃⁻ + 2 Na⁺ + SO₄²⁻ ⇒ BaSO₄ (s) + 2 Na⁺ + 2 NO³⁻
by removing spectator ions (2NO₃⁻ and 2 Na⁺), the net ionic equation :
<em>Ba²⁺ + SO₄²⁻ ⇒ BaSO₄ (s) </em>
<span> buffers resist changes in pH
levels, they are used to regulate biological functions that only occur
at certain pH levels.</span>