Okay
40ml-35ml=5ml
5ml is the volume of the rock
1ml=1cm3
hence the volume of the rock is 5cm3
It's back wards lol you need to take it right
Answer:

Explanation:
Here, we want to calculate the number of formula units in the given molecule
We start by getting the number of moles
To get the number of moles, we have to divide the mass given by the molar mass
The molar mass is the mass per mole
The molar mass of calcium bromide is 200 g/mol
Thus, we have the number of moles as follows:

The number of formula units in a mole is:

The number of formula units in 0.2075 mole will be:
Kc = [H3O+][HCO3-] / [H2CO3]
Remember that Kc is products over reactants. Also, you do not include liquid water in a Kc expression, since liquid water has no concentration.