<u>Explanation:</u>
To calculate the number of moles, we use the equation:
.....(1)
According to mole concept:
1 mole of a compound contains number of particles.
- <u>For A:</u> 2.12 g of potassium bromide
Given mass of KBr = 2.12 g
Molar mass of KBr = 119 g/mol
Putting values in equation 1, we get:
1 mole of potassium bromide contains 1 mole of potassium element and 1 mole of bromide element.
So, 0.0178 moles of potassium bromide will contain number of potassium atoms and
- <u>For B:</u> 0.1488 g of phosphoric acid
Given mass of phosphoric acid = 0.1488 g
Molar mass of phosphoric acid = 98 g/mol
Putting values in equation 1, we get:
1 mole of phosphoric acid contains 3 moles of hydrogen element, 1 mole of phosphorus element and 4 moles of oxygen element.
So, 0.00152 moles of phosphoric acid will contain number of hydrogen atoms, of phosphorus atoms and number of oxygen atoms.
- <u>For C:</u> 23 kg of calcium carbonate
Given mass of calcium carbonate = 23 kg = 23000 g (Conversion factor: 1 kg = 1000 g)
Molar mass of calcium carbonate = 100 g/mol
Putting values in equation 1, we get:
1 mole of calcium carbonate contains 1 mole of calcium element, 1 mole of carbon element and 3 moles of oxygen element.
So, 230 moles of calcium carbonate will contain number of calcium atoms,
- <u>For D:</u> 78.452 g of aluminium sulfate
Given mass of aluminium sulfate = 78.452 g
Molar mass of aluminium sulfate = 342.15 g/mol
Putting values in equation 1, we get:
1 mole of aluminium sulfate contains 2 moles of aluminium element, 3 moles of sulfur element and 12 moles of oxygen element.
So, 0.229 moles of aluminium sulfate will contain number of aluminium atoms, of sulfur atoms and number of oxygen atoms.
- <u>For E:</u> 0.1250 mg of caffeine
Given mass of caffeine = 0.1250 mg = g (Conversion factor: 1 g = 1000 mg)
Molar mass of caffeine = 194.2 g/mol
Putting values in equation 1, we get:
1 mole of caffeine contains 8 moles of carbon element, 10 moles of hydrogen element, 4 moles of nitrogen element and 2 moles of oxygen element.
So, moles of caffeine will contain number of carbon atoms, of hydrogen atoms, of nitrogen atoms and number of oxygen atoms.