Acids and alkalis Flashcards

1
Q

Difference between an acid and alkalis?

A

Acids form H+ ions when they dissolve in aqueous solutions.

Alkalis form OH- ions when they dissolve in aqueous solutions. Alkali is a type of base.

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2
Q

There are two main ways of measuring the pH of a substance:

A

pH probe-numerical figure

Universal indicator-colour

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3
Q

What does litmus paper do?

A

Shows wether something is an acid or an alkali.
Blue in alkali.
Red in acid.
Violet is neutral.

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4
Q

Why does using a pH probe improve the experiment to measure a change in pH?

A

It means you don’t have to judge the colour of each value of pH so there is less dependence on human judgement.
It gives a digital value to 2 decimal places which is more precise than a universal indicator.

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5
Q

Why is tap water an example of a dilute solution?

A

Contains a small quantity of dissolved minerals.

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6
Q

Dilute vs Concentrated Solutions

A

Concentrated
Relatively large amount of solute in given volume
Dilute
Relatively small amount of solute in given volume

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7
Q

Reaction of Metals with Acids

A

When acids react with metals, a hydrogen and a salt are always formed. The first part of the salt’s name comes from the metal involved. The second part of the name comes from the acid.

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8
Q

Neutralisation of Acids

A

Acids can be neutralised by reacting with bases (an alkali is a base that dissolves in water). Metal carbonates, metal oxides and metal hydroxides are all examples of bases.

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9
Q

Separating Mixtures

A

The aim of this practical is to produce a pure, dry sample of a soluble salt from an insoluble oxide or carbonate.

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10
Q

What’a a precipitate reaction?

A

In aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid.

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11
Q

Titration indicators:

Phenolphthalein

Methyl
orange

A

Phenolphthalein
Pink in alkali → colourless in acid.

Methyl orange
Yellow in alkali → red in acid.

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