7 - Acids, Bases & Salts

Question 1

Def. Acid

Answer 1

A substance that gives away/donates hydrogen ions (H⁺). This only happens in a solution with water. H⁺ ions are known as protons.

Question 2

Def. Base

Answer 2

A substance that recives/accepts hydrogen ions (H⁺), or protons, from acids (and they are not necesarily soluble in water)

Question 3

Def. Alkali

Answer 3

A soluble base that accepts protons from acids

Question 4

Def. Strong Acid

Answer 4

An acid with completely disassociated into ions in a solution where no particle in the acid remain molecules

Question 5

Def. Weak Acid

Answer 5

An acid with partially disassociated into ions in a solution where most particles in the acid remain molecules

Question 6

What are the 3 indicators for Acids and Bases?

Answer 6

• Litmus paper
• Thymolphalein
• Methyl Orange

Question 7

What does Litmus paper reveal?

Answer 7

• When in an acid, it turns red
• When in a base, it turns blue
• When in a neutral colour, it remains the same.

There are two colours - red and blue litmus paper

Question 8

What does Thymolphalein reveal?

Answer 8

• It turns blue when reacting with an base
• Otherwise, it remains colourless

It starts of as transparent

Question 9

What does Methyl Orange reveal?

Answer 9

• It turns red when reacting with an acid
• It turns yellow when reacting with anything else such as neutral or bases

It starts of as orange

Question 10

Why will strong acids react faster than weak acids?

Answer 10

They have a larger concentration of hydrogon ions/protons

Question 11

What is produced when an acid and a metal react?

Answer 11

Acid + Metal → a salt + H₂

Question 12

What is produced when an acid and a base react?

Answer 12

Acid + Base → a salt + H₂O

Question 13

What is produced when an acid and a carbonate react?

Answer 13

Acid + Carbnate → a salt + H₂O + CO₂

Question 14

What is the formula for ethanoic acid?

Answer 14

CH₃CO₂H

Question 15

What are the 4 acids you are required to know?

Answer 15

• Hydrochloric acid (HCl)
• Sulfuric acid (H₂SO₄)
• Nitric acid (HNO₃)
• Ethanoic acid (CH₃CO₂H)

Question 16

What solutions do most non-metal oxides form?

Answer 16

Acidic solutions

Question 17

What solutions do most metal oxides form?

Answer 17

Basic solutions

Question 18

What type of oxide does Hydrogen form?

Answer 18

A neutral oxide, aka H₂O/Water

Question 19

What type of oxides do Aluminium and Zinc form?

Answer 19

Amphoteric oxides

Question 20

What is an amphoteric oxide?

And which two elements are used to form them?

Answer 20

They are oxdes that react with both bases and acids - such as Aluminium or Zinc

Question 21

What is the general equation for neutralisation?

Answer 21

H⁺ + OH^- = H₂O

This is the ionic equation for all reactions between acids and bases

Question 22

What is the pH scale and what does it stand for?

Answer 22

A measurement of hydrogen cation concentration

Number n on the scale stands for 1 x 10^-n concentration of H+

Question 23

What are solutions with a higher pH called?

Answer 23

They are Basic, and Alkaline

Question 24

What is the pH for neutral?

Answer 24

7

Question 25

What are solutions with a lower pH called?

Answer 25

Acidic

Question 26

What is the solubility rule for nitrates?

Answer 26

All nitrates are soluble

Question 27

What is the solubility rule for Chlorides?

Answer 27

All common Chlorides are soluble, except for lead and silver chloride

Question 28

What is the solubility rule for Sulfates?

Answer 28

All common Sulfates are soluble, except for barium, calcium and lead sulfate

Question 29

What is the solubility rule for Hydroxides?

Answer 29

Sodium , potassium , ammonium hydroxide are soluble, calcium hydroxide is partially soluble, and the rest of the common hydroxides are insoluble

Question 30

What is the solubility rule for carbonates?

Answer 30

Sodium, potassium, and ammonium carbonate are soluble, while all other common carbonates are insoluble

Question 31

What is the solubility rule for sodium, potassium, and ammonium salts?

Answer 31

They are all soluble

Question 32

What reaction can be used to create a soluble salt, and how would you obtain the crystallised salt?

Answer 32

The reaction of an acid with excess metal will create a soluble salt.

The excess metal can then be filtered away and the filtrate can be boiled to get rid of water.

Question 33

When attempting to create a pure salt using excess metal and acid, why is it important to use excess metal and not acid?

Answer 33

So that acid does not remain, and mix with the salt solution, rendering it impure

Question 34

How do you obtain a salt from an alkali (which is soluble)

Answer 34

You cannot obtain it using excess alkali because the ecxess will dissove in the slution and cannot be fltered. You use a graduated pipette and pipette filler to obtain a specific volume of aqueous alkali, then pour that into a conical flask. Place this beneath a burette flled with acid and pour universl indicator into the flask. Pour acid drop by drop until the solution in the flash goes green (neutral).

Note the volumes used, then repeat experiment without indicator.

Question 35

How does precipitation work?

Answer 35

Two solutions are mixed together to form an insoluble solid called the precipitate.

Question 36

How do you isolate a precipitate from it’s solution?

Answer 36

You

Question 37

What are the 3 steps to make and isolate a precipitate?

Answer 37

1. Mix the reactents to make the ppt, and stir (e.g. with glass rod)
2. Filter the mixture and collect the residue
3. Wash the precipitate with distilled water to get rid of unwanted substances and then dry with filter paper