I need help with some questions and types of problems

[madelineshue]

Hello everyone! I'm a biology major student and I'm really bad at chemistry, but I need to pass an examn in order to continue my studies. I already failed it once and was expelled, I reapplied in hopes of bettering myself. To my surprise no matter how much I try to try, I learn the best when someone else explains things in great detail to me. I suffer from OCD and it greatly affects my studying skills as well.

Could you please provide me with a detailed answer to my questions please? I'd be really greatful if you helped me out!

My questions would be the following:

How does soap clean?
I know the basics of cleaning with soap, but the lecturer is strict with the answers and I really need to hang on to every single point to earn that 70% and pass.
He gave us the following key words he'll be looking for in the correct answer: amphipathic particle, micelle, dissolution - like dissolves like - fat in the apolar part

We have two solutions: 1.7 dm3 of potassium hydroxide solution with a concentration of 0.004 mol/dm3 and 600 cm3 of hydrochloric acid with a concentration of 0.02 mol/dm3. What is the pH of each solution? What will be the pH of the solution obtained by combining these two solutions?
The teacher only gave us the final answer, but I still don't know how to solve it. I'm so lost that I can't even know how should I even approach this problem.
Since it's a general problem for me to calculate pH, I would be delighted if someone could write a step by step explanation on the topic.

A piece of zinc weighing 3.40 g is thrown into 450 cm3 of hydrochloric acid with a concentration of 0.20 mol/dm3. How many cm3 of gas evolve at 45 ºC and a pressure of 940 hPa?
Similarly to the previous question, I'm only given the final answer and no steps on how to solve the problem.

We have 2 solutions: 0.42 liters of nitric acid with a pH of 2.02 and 48.3 cm3 of a strontium hydroxide solution with a concentration of 6.71 mmol/dm3. What is the concentration of the nitric acid solution in mol/m3? What is the pH of the strontium hydroxide solution? What will be the pH of the resulting solution if the above two solutions are mixed and then diluted to 2.0 dm3?
To this question, there were no answers provided (for some reason).

How many kilograms of aluminum do we need to react with excess hydrochloric acid if we want to fill a 5.0 liter gas tank with the developing gas at a pressure of 0.970 atm and a temperature of 42 degrees Celsius?

I generally need help with :

- calculating the pH of solutions
- calculating the concentration of a solution when the pH is given
- calculating the pH when 2 different solutions are mixed together
- problems including thermochemistry
- problems including pressure, universal gas constant and gases in general

Please help me out if you can, I'm desperate at this point, I really don't want to fail again, that would mean the end of my university studies and my dream to become a biologist. The next exam on this will be around the end of October, I want to successfully pass it. If I don't I still have a few exam dates to complete it, but the sooner, the better for me. I have other mandatory subjects that are hard to learn as well. My mental health is really struggling lately due to the exam stress.
I'm happy if you only have links or video recommndations as well!

(Sorry for the grammatical errors, English is my second language.)

[ChenBeier]

1. Soap is made of amphipathic particles, the hydrophil part dissolves in water the hydrophob part in fat or oil. The soap molecules develop micelles. A dirt particle is fatty, so the particle will be surounded from the soap molecules, by stickig the hydrophob part in. The hydrophil part will be in water, so the particle wil moved away.

2. Calculate the mole of each chemical n = c*V
pH = - log(cH+)
14 = pH + pOH

1,7 dm^3 * 0.004 mol/ dm^3 = 0.0068 mol => pOH- = -log(0.0068) = 2,167
pH = 14 -2,167 = 11,83

0,6 dm^3 *0,02 mol/ dm^3 = 0,012 mol => pH = 1,92

For the mixture combine both solution means 0,012 mol - 0,0068 mol = 0,0052 mol
Add the volumes 0,6 dm^3 + 1,7 dm^3 =2,3 dm^3
c= 0,0052 mol/2,3 dm^3 = 0,024 mol/dm^3 => pH= 2,66

3. Calculate the mol of zinc and HCl, need molar mass of Zn, n= m/M
Write the chemical equation.
Look up which is the limiting compound. It will drives the mole of hydrogen.
pV=nRT solve for V

4. Similar calculation as no. 2
Keep in mind strontiumhydroxide is Sr(OH)₂