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Starter for 10

Connect your learning. Starter for 10. Sit back to back – label yourselves A & B. Connect your learning. Starter for 10. Solvent. Connect your learning. Starter for 10. Solution. Connect your learning. Starter for 10. Solute. Connect your learning. Starter for 10. Concentration.

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Starter for 10

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  1. Connect your learning Starter for 10 Sit back to back – label yourselves A & B

  2. Connect your learning Starter for 10 Solvent

  3. Connect your learning Starter for 10 Solution

  4. Connect your learning Starter for 10 Solute

  5. Connect your learning Starter for 10 Concentration

  6. Match up the following words and definitions. Formed when a substance dissolves in a liquid. Solvent How much solute is dissolved in the solvent Solution The liquid part of the solution that the substance dissolves in. Solute The substance that dissolves in the liquid. Concentration

  7. Learning outcomes (c) State how to make a standard soluton (B) Calculate the amount of substance in mol, using solution volume and concentration (A/A*) Calculate the mass of a solute needed to prepare a certain volume of a standard solution

  8. What units are used to measure concentration? mol dm-3 g cm3 mol cm3 dm3

  9. If the volume of the solution is measured in dm3. n = c x V Where • n = amount of substance, in mol • c = concentration of substance, in mol dm-3 • V = volume of solution, in dm3 • NB if the volumes are small (i.e. cm3) divide V by 1000 • Complete question 1 from the text book 1 dm3 = 1000cm3 = 1litre

  10. Standard solutions • Solution of known concentrations • Used in titrations • You will firstly calculate an example and then use your results to make up a standard solution • Use a volumetric flask – two types available, find out what they are and when you should use each type

  11. To calculate a standard solution you need to; • Consider the volume of solution required • Work out the amount, in mol, of solute needed • Convert the amount of solute to a mass, in g, so you know how much to weigh out

  12. Examples • In a solution with a concentration of 4 mol dm-3 there are 4 moles of solute dissolved in every 1 dm3 of the solution. • In 1 dm3 there are 4 mol of dissolved solute • In 2 dm3 there are 8 mol of dissolved solute • In 0.25 dm3 there is 1 mol of dissolved solute • If you know the concentration in mol dm-3, you can find the amount, in mol, in any volume of solution

  13. Worked example Find the mass of KOH required to prepare 250 cm3 of a 0.200 mol dm-3 solution

  14. Worked example Find the mass of KOH required to prepare 250 cm3 of a 0.200 mol dm-3 solution • Find the amount of KOH, in mol, required in the solution: n (KOH) = c x V/1000 = 0.200 x 250/1000 = 0.0500 mol 2. Convert moles into grams Molar mass, M(KOH) = 39.1 + 16.0+ 1.0 = 56.1 g mol-1 Amount n = mass m molar mass M Hence, m = n x M = 0.0500 x 56.1 = 2.805g

  15. Calculate • Find the mass of sodium chloride required to prepare 250cm3 of a 0.300 mol dm-3 solution • When calculated we are going to make up a standard solution based on the results

  16. Molar solutions • Referred to as ‘M’ on bottles e.g. 2M HCl • M means molar and refers to a solution with a concentration in moles per dm-3 • 2 mol dm-3 and 2M means the same thing! • Question 3 from the text book

  17. Homework • Complete questions 1-3 on pages 17 in the text book • Last weeks homework (exam questions, on the wiki lesson 6) – complete questions 1iii and 2ii

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