There is a couple different ways to determine if a bond is ionic orcovalent. By definition, an ionicbond is between a metal and a nonmetal, and a covalent bond is between 2 nonmetals. So you usually just look at the periodic table and determine whether your compound is made of a metal/nonmetal or is just 2 nonmetals.
This question is asking for an element with 5 valence electrons. Just go to the row it is in (excluding transition metals) and count over.
The answer would be c. P
Answer:

Explanation:
The Gibbs free energy in thermodynamics is a potential which is used to calculate maximum of the reversible work which is performed by a specific thermodynamic system at constant temperature (isothermal) as well as pressure (isobaric).
The expression for the change in free energy is:

Answer:
Hydrogen H₂ will be the limiting reagent.
The excess reactant that will be left after the reaction is 3.45 moles.
4.3 moles of water can be produced.
Explanation:
The balanced reation is:
2 H₂ + O₂ → 2 H₂O
By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of each compound participate in the reaction:
- H₂: 2 moles
- O₂: 1 mole
- H₂O: 2 moles
To determine the limiting reagent, you can use a simple rule of three as follows: if by stoichiometry 1 mole of O₂ reacts with 2 moles of H₂, how much moles of H₂ will be needed if 5.6 moles of O₂ react?

moles of H₂= 11.2 moles
But 11.2 moles of H₂ are not available, 4.3 moles are available. Since you have less moles than you need to react with 5.6 moles of O₂, <u><em>hydrogen H₂ will be the limiting reagent</em></u> and oxygen O₂ will be the excess reagent.
Then you can apply the following rules of three:
- If by reaction stoichiometry 2 moles of H₂ react with 1 mole of O₂, 4.3 moles of H₂ will react with how many moles of O₂?

moles of O₂= 2.15 moles
The excess reactant that will be left after the reaction can be calculated as:
5.6 moles - 2.15 moles= 3.45 moles
<u><em>The excess reactant that will be left after the reaction is 3.45 moles.</em></u>
- If by reaction stoichiometry 2 moles of H₂ produce 2 moles of H₂O, 4.3 moles of H₂ produce how many moles of H₂O?

moles of H₂O= 4.3 moles
<u><em>4.3 moles of water can be produced.</em></u>