Two pure elements react to form a compound. one element is an alkali metal, x, and the other element is a halogen, z. which of the following is the most valid scientific claim that can be made about the compound? a. it has the formula xz2
b. it does not dissolve in water.
c. it contains ionic bonds.
d. it contains covalent bonds.

Option c. It contians ionic bonds

Explanation:

Let's take as an example NaCl

An element from group 1 (alkali) with an halogen.

Elements from group 1 form cations with +1 (charge)

This ionic salt, can't never has the formula XZ₂

Ionic salts, also can be dissolved in water, and they don't contain covalent bonds.

C. It contains ionic bonds.

Explanation: Ionic bonds are formed as a result of electrostatic force of attraction between a positively charged ion (cation) and a negatively charged ion (anion).

An alkali metal is a member of the group one elements such as lithium, sodium and potassium which have one electron in their outermost shell while a halogen is a member of group seven elements such as fluorine, chlorine and bromine which have seven electrons in their outermost shell. X will lose its valence electron in order to attain a stable octet or duplet structure thus becoming positively charged while X will gain the electron lost by X in order to attain a stable octet structure thus becoming negatively charged.

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.