Lab Skills and Chemical Analysis S3 UNIT 1 Lab Skills and Chemical Analysis Concentration

Concentration Context for learning: The concentration of a solute is very important in studying chemical reactions because it determines how often molecules collide in solution and thus indirectly determines the rates of reactions. Learning Intentions (WALT): We are learning to: Develop concentration of a solution is the number of moles of solute dissolved in 1 litre (1000 cm3) of solution and the unit is mole per litre (written as mol / l or mol l-1). Develop our knowledge of concentration and how it can be calculated. Understand why it is of central importance in chemistry, and just like density, is an intensive property of a substance unless the ratio of solute to solvent is changed. Prepare a standard solution. Success Criteria(WILF): What I’m looking for: You will be able to determine concentration from number of moles and volume. You will be able to make a standard solution.

New words Meaning GLOSSARY Concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: mass concentration, molar concentration, number concentration, and volumeconcentration. Mole The mole is the unit of amount in chemistry. Solution In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. Solute is a substance dissolved in another substance, known as a solvent. Solvent The component of a solution that is present in the greatest amount. It is the substance in which the solute is dissolved. Examples: The solvent for seawater is water. Saturated The term saturated solution is used in chemistry todefine a solution in which no more solute can be dissolved in the solvent. Standard Solution A solution with an accurately known concentration.

S2 Revision

Units of Volume 1 L = 1 dm3 1000cm3 = 1 dm3

Convert the following 3000cm3 = ________dm3 4.5 dm3 = _________cm3

What is a mole?

Avogadro’s Number 1 mole = 6.02 x 1023 particles

Concentration Concentration of a solution is a measure of the number of particles of solute dissolved in a solvent. Solute - a substance which is dissolved. Solvent - the liquid in which the solute dissolves.

A concentrated solution has a greater number of solute particles than a dilute solution.

Calculating Concentration mol Mol/L or mol/dm3 Litres of dm3

Calculate the concentration of the following solutions… 2 moles of sodium hydroxide in 500 cm3 of solution 0.5 moles of copper chloride in 3 dm3 of solution 2.24 moles of sodium carbonate in 100 cm3 of solution.

Calculate the number of moles in the following solutions… 500cm3 of a 3.5 mol/dm3 solution of HCl 1 dm3 of a 2 mol/dm3 solution of NaOH 0.75dm3 of a 1 mol/dm3 solution of NaOH

Standard Solution

Volumetric Flask There is only one graduation (line) this means that we have, for example, 100 ml of our solution not 100 ml of solvent.

Standard Solution A standard solution is a solution of known concentration.

Your task is to make a 0.1 mol/dm3 solution of copper sulphate for the S1 pupils to use. We have 250 ml volumetric flasks The gram formula mass of copper sulphate is 159.5 g/mol

We know the concentration and the volume, we need to find out how many moles this will take. n = c x V = 0.1 x 0.25 = 0.025 moles

Now we need to calculate the mass Now we need to calculate the mass. We have calculated the required number of moles and we know that the GFM of copper sulphate is 159.5 g. m = n x GFM = 0.025 x 159.5 = 3.98g