Mole
What is a mole? The ‘mole’ is the SI unit for the measurement of large numbers of minute particles. Number of particles in 1 mol is 6.02 x 1023 ……. Symbol =AN. = 602,000,000,000,000,000,000,000. This is named Avagadro number. Fig.1 Mass of a mole.
A simple way to look at it. If you take the atomic mass of any element measured in grams it can be considered as 1 mole of atoms.. Or If you take the molecular mass of a chemical in grams, it will have 1 mole of molecules. Similarly you can take one mole of cat-ions or an-ions and even a mole of photons.
Table 1. This table gives the mass of 1 mole of some elements and the number of particles in each..
AN = 6.02 x 1023 Table 2. This table gives the number of molecules in 1 mole.
Table 3. This table gives the number of radicals in 1 mole.
If you are fond of formulae:- Molarity...."M' This is a unit to show the strength or the concentration of solutions. This is usually given as the number of solute moles dissolved in a litre of a solution. If one ltre of a salt NaCl , solution contains 1 mole of salt; (That is 58.5 g), its molarity will be 1 mol/L ( L for litre) A few questions to practice. 1.0
2.0 Let us tabulate some of these quantities for oxygen, water and salt.
3.0 What is the molecular mole of Sulphur? This is a difficult problem. Sulphur has many types of molecules. The diagram gives a molecule with 8 atoms. Normally 32 g /mol. is used for calculations. Example 1 Find the no. of moles and the no. of molecules in 800g.. of anhydrous Copper sulphate. Answer: Molar mass of CuSO4 = 64+ 32+ 64 = 160g./mol. 160 g.…………………………..1 mol. 800g ………………………… 800/160 mol = 5 mol. 1mol has……………………….AN molecules. 5 mol…………………………...5AN molecules. Highlight to get the answers. Example 2 If you have to weigh the no. of moles in column 1 of the chemicals in row 1 how many grams would you weigh?
1.0 Select the most suitable word for these:-. A Mole, B- Avogadro’s number. C – Molar mass D - Mass of one molecule E- Molarity ..
=5 marks 2..0
2x5=10 marks. 3.0 Complete the blank spaces in this table.
15. marks. 4.0
2x9 = 18marks 5.0 1000 ml of a sodium carbonate solution was made using 106g. of solute. Answer the following: 1 How many moles of Na2CO3 are present in the solution? 2. If you measure out 22 ml of solution into a beaker, what is the molarity of that? 3. How many moles can be obtained by evaporating 250ml of solution? 4. What would be the mass of the residue after evaporating the water? 5. What volume of the solution will have 0.1 moles? 5x5= 25 marks 6.0. This question is regarding the Calcium chloride molecule. CaCl2. Find the following. 4.1 Mass of 1 mol of the chemical compound? 4.2 The number of Ca++ ions in 1 mole of the compound.? 4.3 The number of Cl- ions in the 1 mole of the compound? 4x3=12 marks 7.0 This is the structure of Auric chloride. (Gold (III) chloride. Considering the structural formula given answer the following: 1 Find the molar mass of the compound. 2 Find the mass of gold in 1 mole of the compound. 3 How many Au)+++ ions can you get from 1 mol of the compound? 4. How many Cl- ions can you get from 1 mole of the compound. 5. Write an equation to show how the molecule can break up into ions. 3x5=15 marks SOLUTIONS. 1.0 A Mole, B- Avogadro’s number. C – Molar mass D - Mass of one molecule E- Molarity ..
2.0
3.0 Complete the blank spaces in this table.
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