Analysing water for acids and bases Flashcards Preview

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Flashcards in Analysing water for acids and bases Deck (20):
1

What is the equivalence point of an acid-base reaction?

The point at which chemically equivalent amounts of acid and base, according to the equation, are present.

2

What is the end point of an acid-base reaction?

The point at which the indicator changes colour. The indicator should be chosen so that the end point is close to the equivalence point.

3

What is a standard solution?

A solution of accurately known concentration.

4

What is alkalinity?

Measure of the ability of water to withstand sudden pH change caused by acid input.

5

How is water made more acidic?

Water is made acidic when natural acids or acids that are generated by human activity dissolve in it.

6

How is water made more basic?

Water is made basic when natural bases or bases that are generated by human activity dissolve in it.

7

Why does water need to be analysed?

Water needs close to an optimum pH for many of its uses. Knowing how much acid or base there is, is important when its pH needs to be adjusted.

8

How can water be analysed?

Using a volumetric analysis, which involves solutions of accurately known concentration and careful measurement of volumes.
eg. qualitative: which chemicals are present or quantitative: how much chemicals are present.

9

What is a primary standard?

A sample that is so pure, that its concentration can be accurately calculated from its mass. Substance used to create a standard solution.

10

What is a burette?

A calibrated glass tube that delivers variable volumes accurately. Volume dispensed is the titre. Must be rinsed with substance used.

11

What is a pipette?

A calibrated glass tube that delivers a fixed volume accurately. Must be rinsed with substance used. Holds the alloquit.

12

What is a titre?

The volume delivered by a burette.

13

What is a aliquot?

Volume delivered by a pipette.

14

What is an indicator?

A weak acid whose conjugate acid changes colour.

15

How to calculate the concentration of a standard solution?

1. divide its mass by its given molar mass
2. use formula c= n/v by dividing its mass by amount of volume

16

What are the steps for an acid-base titration?

1. write balanced equation between base and acid, taking not of mole ratio
2. determine the average volume of the titre
3. calculate concentration of standard solution if unknown and then calculate amount of mole
4. using mole ratio determine amount of mole of the unknown
5. using c= n/v, calculate concentration of unknown

17

What would happen to results of a titration when the burette is rinsed with water?

The burette solution is diluted with water so more is used.

18

What is a volumetric flask?

Used prepare standard solutions. Needs to be rinsed with distilled water.

19

What is a conical flask?

Sits underneath burette where titration takes place. Must be rinsed with water. Is the container for the alloquit.

20

Which is the correct way to prepare glassware for a titration?
1. pipette, burette and conical flask should only be rinsed with water
2. pipette should be rinsed with water, burette rinsed with water and solution being analysed
3. conical flask should be rinsed with water and then dried to remove all water
4. both pipette and burette should be rinsed with water then the solution being analysed

4. both pipette and burette should be rinsed with water then the solution being analysed.
This means that they will both contain only the moles of the solution being analysed and there will be not over or underestimation.