<h3>Answer:</h3>
4 mol O₂
<h3>General Formulas and Concepts:</h3>
<u>Math</u>
<u>Pre-Algebra</u>
Order of Operations: BPEMDAS
- Brackets
- Parenthesis
- Exponents
- Multiplication
- Division
- Addition
- Subtraction
<u>Chemistry</u>
<u>Atomic Structure</u>
<u>Stoichiometry</u>
- Using Dimensional Analysis
<h3>Explanation:</h3>
<u>Step 1: Define</u>
[RxN - Balanced] CH₄ + 2O₂ → CO₂ + 2H₂O
[Given] 4 mol H₂O
[Solve] x mol O₂
<u>Step 2: Identify Conversions</u>
[RxN] 2 mol H₂O → 2 mol O₂
<u>Step 3: Stoichiometry</u>
- Set up conversion:

- Multiply/Divide:

(l ) the mass ratios of the substances in the reaction
<u>(2) the mole ratios of the substances in the reaction</u>
(3) the total number of electrons in the reaction
<span>(4) the total number of elements in the reaction</span>
Answer: The nuclide symbol of X is 
Explanation:
The given nuclear reaction is a type of alpha decay process. In this process, the nucleus decays by releasing an alpha particle. The mass number of the nucleus is reduced by 4 units and atomic number is also decreased by 2 units. The particle released is a helium nucleus.
The general equation representing alpha decay process is:

For the given equation :

As the atomic number and mass number must be equal on both sides of the nuclear equation:

Thus the nuclide symbol of X is 
Quantum states of electrons are usually written in terms of four numbers: the principle quantum number (n), the angular momentum azimuthal number (L), the magnetic quantum number (ml), and the spin projection number (ms). The quantum number set (4,1,0,+1/2) and (4,1,1,+1/2) share the same principle quantum numbers and therefore both sit in the n=4 electron shell.
1) The time depends on what the lab wanted you to do. It will tell you in the procedure when you are supposed to considered a reaction to be complete and you just measure the time for that to happen.
2) Most text books say that increasing the concentration of one or more reactants will increase the rate of the reaction. To prove this with your data you need to show that when you increased the concentration of one of the reactants, the reaction rate did increase. The results of this experiment are not enough to make a general statement since the experiment was not on a large enough scale to diffidently prove anything. (you could have been testing the one exception or had a error in one of your trials)
I hope this helps. Let me know in the comments if anything is unclear.
(The concentration of one or more of the reactants will increase the rate of the reaction. This is explained through the fact that all reactions require collisions that have certain orientations and a minimum energy level. By increasing the concentration of one or more reactants, you increase the number of collisions which increases the rate since requires collisions in order to occur.) <span />