Acids and Bases

Question 1

Classify acids and bases as chemicals with distinct properties and uses:

Answer 1

Acids:
Tastes sour
Releases H+ ions
Corrosive
Rough texture
pH below 1-6
turns litmus red
turns universal indicator: red, orange, yellow
keeps phenolphthalein colourless

Bases:
Tastes bitter
Alkalies: Releases OH- ions
Corrosive
Soapy slippery texture
pH above 8-14
turns litmus blue
turns universal indicator: blue, dark green, purple
turns phenolphthalein pink

Question 2

State the name and formula of some common acids and bases

Answer 2

Acids
- Hydrochloric acid - HCL
- Nitric acid - HNO3
- Sulfuric acid - H2SO4

Bases
- Sodium hydroxide - NaOH
- Potassium hydroxide - KOH
- Calcium hydroxide - Ca(OH)2
- Ammonia - NH3
- Calcium carbonate - CaCO3

Question 3

Recognise what happens when acids and bases react together

Answer 3

Acids and bases react to neutralise each other

Question 4

Use the pH scale to compare the acidity and alkalinity of different solutions

Answer 4

The pH scale as running from 0-14, with zero the most acidic and 14 the most alkali, and 7 neutral.

Question 5

Use indicators to classify solutions as acidic, alkaline or neutral:

Answer 5

Phenolphthalein
acid: colourless
base/alkali: pink
neutral: colourless

Litmus paper
acid: red
base/alkali: blue
neutral: purple

Universal indicator
acid: red, orange, yellow
base/alkali: dark green, blue, purple
neutral: light green

Question 6

What is salt a compound of

Answer 6

Salt is a compound of a metal ion and one or more non-metal ions (not oxide)

Question 7

What is salt

Answer 7

Salts are neutral substances that can be formed during neutralisation reactions, and consist of one metal and one or more non-metal element. They can be soluble or insoluble in water.

Question 8

Explain how water is formed from H+ and OH- ions when acids neutralise bases

Answer 8

Acids give off H+ ions, and bases/alkali give off OH- ions. These combine to form H2O.

Question 9

State the general equation for acid and base neutralisation

Answer 9

Acid + Base –> Salt + Water

Question 10

Describe some techniques for preparing salts in the laboratory

Answer 10

• Growing crystals
  Add 50mL of H2SO4 into a beaker. Light the bunsen burner up and place the tripod on top of the burner and place the gauze on top of the tripod which will have the beaker on top. With a thermometer measure the H2SO4 to 70 degrees. When it is at 70 degrees turn the bunsen burner off and carefully put the beaker on the tile. Slowly add CuO until the solution is saturated. Place the filter paper over a funnel and place the funnel over another beaker. Carefully pour the solution into the funnel. With the filtered solution pour it into a petri dish. Place the petri dish somewhere to turn into crystals.

CuO (s) + H2SO4 (aq) –(heat)–> CuSO4 (aq) + H2O

Question 11

Construct word equations for neutralisation reactions

Answer 11

(acid + base [metal oxide or metal hydroxide] only)

Question 12

Write balanced symbol equations for acid-base neutralisation reactions.

Question 13

State the general equation for acid and metal carbonate neutralisation

Answer 13

Acid + Metal carbonate –> Salt + Water + Carbon dioxide

Question 14

State the names and formulae of some common carbonates

Answer 14

Sodium Carbonate - Na2CO3
Calcium Carbonate - CaCO3

Question 15

Write balanced symbol equations for acid-carbonate reactions

Question 16

State Collision theory

Answer 16

For a reaction to occur between two substances, their particles must collide with each other. The more collisions that occur per second, the faster the reaction.

Question 17

Explain the effect of temperature on reaction rate using collision theory

Answer 17

Reactions go faster when they’re hotter. When you increase the temperature you give particles more kinetic energy and so more collisions occur per second.

Question 18

Explain the effect of surface area on reaction rate using collision theory

Answer 18

If more surface area is available more particles collide which means a faster rate of reaction.

Question 19

Explain how to make your own indicators from plants

Answer 19

Get your selected plant and chop it up. Add material in a morter and add water and sand and thoroughly grind it. Filter the solution. Place HCL and NaOH into 2 seperate dips in the spot tiles. Add a few drops of the solution in the acid and base and record the colour differences.

Question 20

Explain how to find your indicator’s pH change point

Question 21

What is an indicator

Answer 21

Define an indicator as a natural dye that changes colour depending on whether it is
placed in an acid or base

Question 22

Show the chemical reactions for 3 ways to produce salt

Answer 22

1. Acid + Base –> Salt + Water
2. Acid + Metal –> Salt + Hydrogen
3. Acid + Metal carbonate –> Salt + Water + Carbon dioxide