Yes it’s correct.
An ionic bond is the transfer of electrons from a metal to a non-metal.
The answer is 3). This is because elements are the simplest form of a substance, and cannot be broken down any further. Compounds on the other hand are much more complex than elements and can be broken down INTO elements.
For example, Na, sodium, is an element and cannot be broken down further. H2O, water, is a compound and can be broken down into Hydrogen and Oxygen.
Answer:
Yes, Mass is conserved.
Explanation:
Every chemical reactions obey the law of conservation of mass. The law of conservation of mass states that in chemical reactions, mass is always constant.
Equation:
2Na + Cl₂ → 2NaCl
From the equation above, one can observe that the reaction started using 2 atoms of Na and it produced 2 atoms of the same element in NaCl. A molecule of Cl produced 2 atoms of Cl in the NaCl
Design a simple experiment to support your answer:
Aim: To demonstrate the law of conservation of mass
One Na atom weighs 23g
Two Na atom will weigh 2 x 23 = 46g
1 atom of Cl is 35.5g
1 molecule of Cl containing two atoms of Cl will weigh 2 x 35.5 = 71g
Total mass of reactants = mass of 2Na + 1Cl₂ = (46 + 71)g = 117g
On the product side, Mass of 1 NaCl = 23+ 35.5 = 58.5g
Two moles of NaCl will give 2 x 58.5g = 117g
Since the mass on both side is the same, one can say mass is conserved.
Answer: 
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
The balanced chemical reaction for nitrogen and hydrogen react to form ammonia:
(1)
The balanced chemical reaction for ammonia and oxygen react to form nitric acid and water:

(2)
The net chemical equation for the production of nitric acid from nitrogen, hydrogen and oxygen by adding 1 and 2

Answer:
5.00g
Explanation:
Molarity is moles per liter
Therefore:
x moles/.250L = .5 moles/1L
Solve for x: .125 moles required
Question asks for grams of NaOH so multiply the moles by the molar mass of NaOH
.125(39.997) = 4.999625g
Rounds to 5.00g