HELP 1. A student determines that the number of grams in a sample of Al2O3 is 18.3 grams. How many moles are in the sample?

2. A chemist needs 35 grams of CaO for a chemical reaction. How many moles of CaO are needed for the chemical reaction?

3. For an acid-base titration, 126 grams of H2SO4 were needed. How many moles of H2SO4 were needed for the Laboratory Activity?

4. A student needs 100 g of vinegar (CH3COOH) for a lab activity. How many moles does the student need?

Explanation:

1)

Given data:

Mass of Al₂O₃ = 18.3 g

Number of moles = ?

Solution:

Number of moles = mass/molar mass

Number of moles = 18.3 g/ 101.96 g/mol

Number of moles =0.18 mol

2)

Given data:

Mass of CaO needed = 35 g

Number of moles = ?

Solution:

Number of moles = mass/molar mass

Number of moles = 35 g/ 56 g/mol

Number of moles =0.625 mol

3)

Given data:

Mass of H₂SO₄  needed = 126 g

Number of moles = ?

Solution:

Number of moles = mass/molar mass

Number of moles = 126 g/ 98.1 g/mol

Number of moles = 1.28 mol

4)

Given data:

Mass of vinegar = 100 g

Number of moles = ?

Solution:

Number of moles = mass/molar mass

Number of moles = 100 g/ 60.1 g/mol

Number of moles = 1.66 mol

the dissolution of polymer can be thermodynamically described in 2 steps.