Answer:
1)
2) The dependent variable = The time it takes for one pendulum swing
3) The independent variable = The length of the pendulum string with weight at the bottom
Explanation:
The relationship between the length of the pendulum string and the time it takes for one pendulum swing is giving as follows;

Where;
T = The period of oscillation = The time to complete one oscillation =Two swings of the pendulum
L = The length of the pendulum
g = The acceleration due to gravity
Therefore, the time it takes for one pendulum swing is directly proportional to the square root of the length of the pendulum
The dependent variable = The time it takes for one pendulum swing
Th independent variable = The length of the pendulum string with weight at the bottom.
Litmus is an indicator
Charged particles are ions
Acids contain H+ ions
Bases contain OH - ions
Hydronium ions are H3O+
Now, I have to take issue with the last one
A base of pH 14 is not a strong base, it would be a highly concentrated base. A strong base is a base that completely deionizes in water.
But technically, for the purpose of your answer strong base = pH 14
Answer: pH is 1.6
Explanation: Explanation: HCl is strong acid and it protolyzes totally:
HCl + H2O ⇒ H3O+ + Cl-
Concentrations are same: [H3O+] = c(HCl)
pH = - log[H3O+] = - log(0.025) = 1.60