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Titration ClassAct SRS enabled. In this presentation you will: Explore the titration method to find the concentration of a solution.

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Presentation on theme: "Titration ClassAct SRS enabled. In this presentation you will: Explore the titration method to find the concentration of a solution."— Presentation transcript:

1 Titration ClassAct SRS enabled. In this presentation you will: Explore the titration method to find the concentration of a solution

2 Titration Titration is a method of analysis that allows us to determine the precise equivalence point of a reaction and therefore the precise quantity of reactant added to the titration flask. From this information we can calculate the concentration of the reactant. To learn about the titration method, it is important to understand first what the pH level of a base or an acid is. Next >

3 Titration The concentration of hydrogen ions in an acid aqueous solution can be measured with the pH scale, where the pH value is the negative logarithm of the oxonium ion concentration: pH Scale The concentrations of hydrogen ions in most acid aqueous solutions are between mol dm -3 and 1 mol dm -3. Therefore, the range of values of these solutions are between 0 and 14 since: –log10(1) = 0 and –log10( ) = 14. pH = -log[H 3 O + ] H + concentration moles per liter Sodium hydroxide Potassium hydroxide Borax Sodium bicarbonate Distilled water Boric acid Vinegar Lemon juice Nitric acid pH values of some substances Magnesia milk Hydrochloric acid Next >

4 Titration The pH of any solution when the concentration of hydrogen ions is written as 1 x 10 -n will be the numeric value of n. pH Scale Pure water at 25 ºC has a concentration of hydrogen ions of 1 x mol dm -3, hence a pH of 7. Every solution of pH 7 is neutral. For example: 1 x mol dm -3 = pH 9. The higher the pH of a solution, the more basic or alkaline it is. The lower the pH, the more acidic it is. Sodium hydroxide Potassium hydroxide Borax Sodium bicarbonate Distilled water Boric acid Vinegar Lemon juice Nitric acid pH values of some substances Magnesia milk Hydrochloric acid H + concentration moles per liter Next >

5 Titration 1 What is the pH value of a neutral solution? Question A) 0 B) 1 C) 7 D) 14

6 Titration Some chemical substances react to different pH levels by changing their color. Indicators These substances, called indicators, are used in titration experiments to establish the acidic-alkaline values of substances and mixtures. Next >

7 Titration Indicators Other indicators change color at different acid-alkaline levels. By selecting the right indicator we can establish the pH level of nearly any aqueous colorless solution. For example, the litmus indicator will show red in acid solutions and blue in basic solutions. Different colorant indicators have different color combinations which change at different pH levels. One color will represent an acidic solution and the other color a more basic solution. Next >

8 Titration 2 What is an indicator used for in a titration experiment? Question A) To establish the acidity-alkalinity of a solution. B) To increase the acidity of a solution. C) To increase the alkalinity of a solution. D) To alter the pH level of a solution.

9 Titration Titration is a laboratory technique used to determine the concentration C r of an acid or base solution. Titration The aim of the experiment is to find out the volume V s of a titrating substance (with a known concentration C k ) necessary to neutralize the acidity or alkalinity of a substance. With the volume of the titrating substance and its concentration, the number of moles necessary to neutralize the substance can be calculated. Next >

10 Titration In a titration, an acid solution of accurately known strength called standard acid is gradually added to a known volume of base until a pH meter reads exactly 7 or an indicator pigment dissolved in the mixture changes its color. The change of color of the indicator signifies the reaching of the equivalence point, where the substances neutralize each other. Next >

11 Titration The unknown concentration of the base can then be calculated based on the number of moles necessary to neutralize each other, together with the base volume, with the equation: where C r is the concentration of the base solution, N r is the neutralizing number of moles, and V r the volume of the titrated solution. Next >

12 Titration 3 What is the final aim of a titration experiment? Question A) To find out the volume of the titrating substance added to the titrated solution. B) To find out the concentration of the titrating substance added to the titrated solution. C) To find out the volume of the titrated solution. D) To find out the concentration of the titrated solution.

13 Titration Calculating Concentration 25 cm 3 of a base changed color (was neutralized) when 15.8 cm 3 of a mol dm -3 acid was added. number of moles N r = volume in dm 3 V r x acid concentration in mol dm -3 C r To calculate the unknown concentration C r of the titrated solution, the number of moles in the acid which neutralized the solution needs to be calculated first. This is given by: So the acid’s moles in this experiment = = 3.95 x mol Next >

14 Titration 4 How is the number of moles of a titrating substance calculated? Question A) Divide the volume by its molarity concentration. B) Multiply the volume by its molarity concentration.

15 Titration Calculating Concentration Knowing the number of moles that were necessary to neutralize the base solution, its concentration can be calculated. Base moles N r = volume in dm 3 V r x acid concentration in mol dm -3 C r 3.95 x mol = (25 dm 3 / 1000 ) x C r Therefore; Applying the moles formula to the base solution, we obtain: 3.95 x mol The concentration of the base solution is therefore mol dm -3 Next >

16 Titration 5 How is the concentration of a titrated solution calculated? Question A) Multiplying the concentration of the titrating substance by its volume. B) Multiplying the number of moles in the titrating substance by its volume. C) Dividing the concentration of the titrating substance by its volume. D) Dividing the number of moles in the titrated substance by its volume.

17 Titration Titration curves The titration of a strong acid with a strong base produces the titration curve shown in the diagram. The curve is drawn by plotting the data obtained during the titration, titrant volume on the x-axis and pH on the y-axis. A titration curve is a graph representing the pH change in a unknown solution during a titration experiment. The titration of a strong base with a strong acid will produce a descending curve in the pH axis. Next >

18 Titration Titration curves 4. The pH range at equivalence. 1. The initial pH of the solution. The important features of titration curves are: 2. The equivalence point when equimolar amounts of both acid and base are present. 5. The final pH. Initial pH Final pH 3. The volume of titrating liquid required for equivalence. equivalence pH range Equivalence point Equivalence titrating volume Next >

19 Titration 6 What does a titration curve represents? Question A) The change of the equivalence point of an unknown solution during a titration experiment. B) The change of the number of moles in an unknown solution during a titration experiment. C) The pH change in an unknown solution during a titration experiment. D) The molarity change in an unknown solution during a titration experiment.

20 Titration Show knowledge and understanding of what a titration experiment is. Show knowledge and understanding of the pH scale. Having completed this presentation you should be able to: Summary Show knowledge of what indicators are. Show understanding of how to calculate the concentration of a solution. End >


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