Which substances are harder than apatite, but softer than corundum?

a. fluorite and quartz

b. topaz and quartz

c. diamond and quartz

d. talc and gypsum

B. topaz and quartz

Explanation:

Hardness of a mineral is measured using Moh’s scale.

Hardness depends on the bonding attraction between the atoms and the size of the atoms present in the mineral

Mineral    Hardness(Moh’s)

Talc                              1

Gypsum                      2

fluorite                        4

Apatite                        5

Topaz                           8

quartz                          7

Corundum                   9

Diamond             10

Option B topaz and quartz  is the Answer

3

explanation:

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%