How many moles of Ca are in 7.2x10^25 molecules of Ca
(show work)

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

We have the final answer as

Hope this helps you

D, E, A, B, C

Explanation:

The weakest base would be Cl- because HCl is a stronger acid than that of H3O+ from which the water is formed.

Also, for NH3 is a stronger acid than +NH4. Reason is that oxygen is more electronegative than nitrogen and thus NH3 is a stronger acid than NH4+.

The stronger, the acid, the weaker its conjugate base. Thus, NH3 is a weaker base than NH4.

NH2- has the highest basicity because nitrogen is less of an electronegative element than is oxygen. Therefore, it will not want a negative charge.

Hence, the final order in terms of increasing basicity is;

Cl-, H20, NH3, NH4, NH2-