B. 1, 2, 1, 2. You balance the equation by making sure there are equal elements on both sides.
Answer: 0.055 moles of 
are produced by the reaction of 0.055 mol of ammonium perchlorate.
Explanation:
The balanced chemical reaction for decomposition of ammonium perchlorate is:
According to stoichiometry :
2 moles of 
produce = 2 moles of
Thus 0.055 moles of will produce =
of
Thus 0.055 moles of are produced by the reaction of 0.055mol of ammonium perchlorate.
Answer:
1.634 molL-1
Explanation:
The mol ration between NH3 and HCl is 1 : 1
Using Ca Va / Cb Vb = Na / Nb where a = acid and b = base
Na = 1
Nb = 1
Ca = 0.208 molL-1
Cb = ?
Va = 19.64 mL
Vb = 25.00mL
Solving for Cb
Cb = Ca Va / Vb
Cb = 0.208 * 19.64 / 25.0
Cb = 0.1634 molL-1 (Concentration of diluted ammonia solution)
Using the dilution equation;
C1V1 = C2V2
Initial Concentration, C1 = ?
Initial Volume, V1 = 25.00 mL
Final Volume, V2 = 250 mL
Final Concentration, C2 = 0.1634 molL-1
Solving for C1;
C1 = C2 * V2 / V1
C1 = 0.1634 * 250 / 25.00
C1 = 1.634 molL-1
The answers are name: Cerium, symbol: Ce, atomic number: 58, and atomic mass: 140.110
These are the answer options of this question and the comments about their validity:
<span>A) It dictates that the number of molecules on each side of a chemical equation must be the same.
False: the number of molecules can change. Take this simple reaction for example:
2H2(g) + O2 -> 2H2O
You start with 3 molecules, 2 molecules of H2 and 1 molecule of O2, and end with 2 molecules of water. Then the number of molecules of each side is different.
B) It dictates that the number of atoms of each element must be the same on both sides of a chemical equation.
TRUE: in a chemical reaction the atoms remain being the same at start and at the end of the process. Given that each atom has a characteristic mass, their conservation implies the law of conservation mass.
C) It states that the mass of the reactants must remain constant in order for a chemical reaction to proceed.
FALSE. The mass of the reactants changes during a chemical reaction, while they transform into the products.
D) It does not apply to chemical reactions.
FALSE: It is an important law used in the calculus related with chemical reactions.
</span>
