A, B and D should be the ones you should check
Answer:

This is a double displacement reaction, C goes with Cl in the products side and O2 goes with H. All that is left is to balance the equation, making sure each side has equal amounts of atoms.
Given information : Sample of 
We need to find the moles of Chlorine in the given sample.
We can say that we need to find moles from the given atoms.
Relation between mole and atom is given by : 
Where
is Avogadro number.


On solving the above equation , atoms(unit) gets cancelled out and we get 0.0286 mol.
In the given sample the moles of Chlorine (Cl) is 0.0286 mol , so option A is correct.
I suppose it could be <span>Xenon, but I'm not pretty sure about this.</span>
Answer:
The answer to your question is P2 = 342 kPa
Explanation:
Data
Pressure 1 = P1 = 155 kPa
Volume 1 = V1 = 22 l
Pressure 2 = P2 = ?
Volume 2 = V2 = 10 l
Temperature = constant
Process
1.- Write the equation of the combined gas law
P1V1/T1 = P2V2/ T2
Cancel T1 and T2 because they measure the same
P1V1 = P2V2
-Solve for P2
P2 = P1V1/V2
2.- Substitution
P2 = (155 x 22) / 10
3.- Simplification
P2 = 3410 / 10
4.- Result
P2 = 342 kPa