F2 - SEM2 - Common acids and alkalis - 9.2 Distinguish acids and alkalis Flashcards by Reggie YIM | Brainscape

Q

What are the tools that help to distinguish between acids and alkalis?

A

Natural indicators
Litmus
Universal indicators
pH meter and data logger

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Q

Give examples of natural indicators and how they responds to acidic, neutral and alkaline solution.

Natural indicators

A

Red cabbage leaves - neutral: purple/blue, acidic: red/pink, alkaline: green/yellow
Red rose petals - neutral: colourless, acidic: red/pink, alkaline: brown/yellow
Hibiscus petals - neutral: pink, acidic: red/orange, alkaline: yellow
Grape skins - neutral: red, acidic: red, alkaline: dark brown / black

Natural indicators

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Q

What are in the plants show different colours in acidic and alkaline solutions

Natural indicators

A

plants contains pigments which show different colours in acidic and alkaline solutions

Natural indicators

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Q

True of False?

Grape skins is a natural indicator for testing of acidity

Natural indicators

A

False
red in colour when the solution is neutral and acidic

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Q

What is the commonly used acid-alkali indicator in the laboratory?

A

Litmus

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Q

What are the 2 types of litmus and how do they respond to acidic and alkaline solution?

Litmus

A

blue litmus (acidic) - neutral and alkaline: blue, acidic: red
red litmus (alkaline) - neutral and acidic: red, alkaline: blue

Litmus

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Q

True of False?

Litmus are only available in paper forms

Litmus

A

False
Litmus are available in solution and paper forms

Litmus

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Q

What is pH value?

Universal Indicator and pH value

A

indicate the relative acidity or alkalinity of substance

Universal Indicator and pH value

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Q

What is pH value ranges / pH scale?

Universal Indicator and pH value

A

0 to 14

Universal Indicator and pH value

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Q

What is pH value of acidic substances, neutral substances and alkaline substances?

Universal Indicator and pH value

A

acidic substances - pH value lower than 7, colour from dark red to yellow (0 to 6)
neutral substances - pH value 7, light green colour
alkaline substances - pH value higher than 7, colour from dark purple to green (14 to 8)

Universal Indicator and pH value

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Q

What is the main difference between litmus and universal indicator?

Universal Indicator and pH value

A

litmus - determine if it is acidic or alkaline
universal indicator - determine relativie acidity or alkalinity or pH value

Universal Indicator and pH value

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Q

What is the pH value of substances below?

lemon juice, orange juice, coffee, milk, tap water, egg white, baking soda solution, bleach, oven cleaner, drain cleaner

Universal Indicator and pH value

A

lemon juice - pH2 > orange juice - pH3 > coffee - pH5 > milk - pH6
tap water - pH7
egg white - pH8 > baking soda solution - pH10 > bleach - pH12 > oven cleaner - pH13 > drain cleaner - pH14

Universal Indicator and pH value

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Q

How to find out the pH value with universal solution?

Universal Indicator and pH value

A

compare the colour of universal solution with pH colour chart

Universal Indicator and pH value

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Q

What is a pH meter?

pH meter and data logger

A

electronic instrument used to measure pH value of solution

pH meter and data logger

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Q

Explain how to measure pH of a solution using pH meter

pH meter and data logger

A

Calibration is necessary before use
Probe of meter is put into solution
Display pH value on the screen

pH meter and data logger

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Q

Explain the function of connecting a data logger to pH sensor

pH meter and data logger

A

similar to a pH meter
record the change in pH of a solution over a period of time

pH meter and data logger

Q

Compare universal indicator and pH meter

pH meter and data logger

A

univeral indicator
advantages
* convenient (no need calibration)
* less solution is needed
disadvantages
* less accurate and less precise - match colour with pH colour chart)
* no suitable for dark-coloured solutions

pH meter
advantages
* more accurate and precise (accurate to 1 to 2 decimal places)
* suitable for solution of any colours
disadvantages
* calibration is needed
* more solution is needed for measurement

pH meter and data logger