Concentration and Titrations PDF

Do Now Activity 1.Calculate the RFM of CaCl2. 2.How do we calculate moles? 3.How do we calculate concentration 4.Convert 250cm3 into dm3  Do Now Activity Complete the worksheet from yesterday. Please do this silently KQ: How do we calculate the concentration of an unknown solu...

Do Now Activity 1.Calculate the RFM of CaCl2. 2.How do we calculate moles? 3.How do we calculate concentration 4.Convert 250cm3 into dm3  Do Now Activity Complete the worksheet from yesterday. Please do this silently KQ: How do we calculate the concentration of an unknown solution? 3 Warm up Review 1. Calculate the RFM of CaCl2. 111 2. Moles = Mass ÷ Mr 3. Concentration = Mass (or moles) ÷ Volume 4. 250 ÷ 1000 = 0.25dm3 4 What is concentration? What does the word concentration mean? Why is the drink on the right more concentrated? Source: Glasses with cordial images, Mrs. Begum 5 What is concentration? Concentration is a measure of how many particles of solute are dissolved in a given volume of solvent. The given volume is usually 1 dm3 (1000cm3). A more concentrated solution has more particles per dm3. The unit for concentration is normally g/dm3. 6 Concentration= mass ÷ volume (dm ) 3 (g/ dm 3) Or Concentration= moles ÷ volume (dm ) 3 (Mol/dm ) 3 Independent practice 1. What mass of HCl is dissolved in 100 cm³ of a 3 M solution? 2. What mass of NaOH is in 24 cm³ of a 2 M solution? 8 Independent practice review 1. What mass of HCl is dissolved in 100 cm³ of a 3 M solution? A 3 M solution contains 3 x 36.5 = 109.5 g. That equals 109.5g in 1000 cm³. From the question, we are looking for the mass in 100 cm 3, Divide answer by 10 to get 10.95 g (in 100 cm 3) 2. What mass of NaOH is in 24 cm³ of a 2 M solution? A 2 M solution of NaOH = 2 x 40 = 80 g 80 g in 1000 cm3 ÷1000 = 0.08 g in 1 cm³ x24 = 1.92 g (in 24 cm³) 9 Independent practice 1. The student made 500 cm3 of a solution of HCl of concentration 0.0500 mol/dm3 Calculate the mass of HCl required. 2. The student made 500 cm3 of a solution of NaOH of concentration 0.1mol/dm 3 Calculate the mass of NaOH required. 3. The student made 50 cm3 of a solution of HCl of concentration 0.025 mol/dm 3 Calculate the mass of HCl required. 4. The student made 200 cm3 of a solution of H2SO4 of concentration 0.06 mol/dm3 Calculate the mass of H2SO4 required. 10  What is a titration? The method of titration 11 What is a titration? Titration is an experimental technique where a solution with a known concentration is used to determine the concentration of an unknown solution. acid (aq) + alkali (aq) ➜ salt (aq) + water (l) NaOH (aq) + HCl (aq) ➜ NaCl + H2O 1 : 1 12  Burette Funnel Conical flask Indicator - Pipette filler phenolphthalein Glass pipette White tile Source Mr Campbell 13 Burette Accurate at measuring varying volumes. More accurate than a measuring cylinder Can add solutions one drop at a time 5 70 cm 3 Mysid wikicommons. Source Mr Campbell 14  23 95cm 3. Source Mr Campbell 15 Glass pipette Accurate at measuring a fixed volume. Source Mr Campbell 16 Titration method 1.The burette is filled with an acid of an unknown concentration. 2.A glass pipette is used to add 25cm3 of a known concentration of alkali to a conical flask. 3.An indicator is added to the alkali and the conical flask is placed on a white tile under the burette. Source Mr Campbell 17 Titration method 4. An initial reading is taken from the burette. 5. The acid is added into the alkali while swirling the conical flask. 6. When the indicator changes colour the reaction has reached its end point. 7. A final reading is taken from the burette and the volume added calculated. Source Mr Campbell 18 Titration method 8. Repeat the titration but this time adding dropwise near the end point. 9. Repeat until you achieve two concordant results. Source Mr Campbell 19 Which piece of equipment is very accurate at measuring a fixed volume? e.g. 25cm3 Burette Measuring cylinder Glass pipette Conical flask 20 Which piece of equipment is very accurate at measuring varying volumes? Burette Measuring cylinder Glass pipette Conical flask 21 Why is universal indicator not used in a titration? It’s too sensitive It doesn’t give a clear end point The colour is too bright It can be used 22 Why is the flask swirled as the acid is added? To make the colour easier to see To fully react the acid and alkali To increase the temperature It’s good exercise 23 24  What is a titration? The method of titration Explaining method 25