Answer: 4
Explanation:
4 is the only one that has to products as well as having the plus at the bottom
1. ₉¹⁹F
2. Mg(OH)₂
3. 2H₂ + O₂ ⇒ 2H₂O
<h3>Further explanation</h3>
1. Fluorine, atomic number : 9 , mass number = 19
Symbol : ₉¹⁹F
protons=electrons=atomic number = 9
neutrons = mass number - atomic mass

Configuration : [He] 2s² 2p⁵
2. Magnesium hydroxide is an ionic compound and is a strong base consisting of 2 ions:
Positive ion: Magnesium: Mg²⁺
negative ion: Hydroxide: OH⁻
The charges of the two are crossed, so that the compound becomes:
Mg(OH)₂
3. Reaction :
H₂ + O₂ --------> H₂O
give coefficient :
aH₂ + bO₂ --------> H₂O
H, left = 2a, right 2⇒2a=2⇒a=1
O, left = 2b, right 1⇒2b=1⇒b=0.5
Reaction becomes :
H₂ + 0.5O₂ --------> H₂O x 2
2H₂ + O₂ --------> 2H₂O
Answer:
1 = oxidation
2 = reduction
Explanation:
Oxidation:
Oxidation involve the removal of electrons and oxidation state of atom of an element is increased.
2I- ----> I₂+ 2e⁻
Reduction:
Reduction involve the gain of electron and oxidation number is decreased.
F + e⁻ ----> F⁻
Consider the following reactions.
4KI + 2CuCl₂ → 2CuI + I₂ + 4KCl
the oxidation state of copper is changed from +2 to +1 so copper get reduced.
CO + H₂O → CO₂ + H₂
the oxidation state of carbon is +2 on reactant side and on product side it becomes +4 so carbon get oxidized.
Na₂CO₃ + H₃PO₄ → Na₂HPO₄ + CO₂ + H₂O
The oxidation state of carbon on reactant side is +4. while on product side is also +4 so it neither oxidized nor reduced.
H₂S + 2NaOH → Na₂S + 2H₂O
The oxidation sate of sulfur is -2 on reactant side and in product side it is also -2 so it neither oxidized nor reduced.
Answer: , 4 molecules of ammonia, NH3(g) is produced; 2 molecules of ammonia, NH3(g) is produced respectively
Explanation:
The balanced equation is stated below N2(g) + 3H2(g) → 2NH3(g)
1 mole of N2(g) reacts with 3 moles of H2(g) to yield 2 moles of NH3(g)
1) If 2 molecules of N2 react, then the balanced equation will be
2N2(g) + 6H2(g) → 4NH3(g)
Thus, 4 molecules of ammonia, NH3(g) is produced
2) If 3 molecules of H2 react, then the balanced equation will be
N2(g) + 3H2(g) → 2NH3(g)
Thus, 2 molecules of ammonia, NH3(g) is produced