Acids, Bases and Alkalis

Question 1

What are the roles of indicators?

Answer 1

to distinguish whether a solution is acidic or alkaline.

Question 2

What is red/blue litmus paper?

Answer 2

a paper that you can dip into a solution and will change colour. red litmus paper turns blue in alkaline solutions and blue litmus paper turns red in acidic solutions.

Question 3

What is phenolphthalein?

Answer 3

a indicator that you can drop into a solution: turns colourless in acidic solutions and pink in alkaline solutions.

Question 4

What is methyl orange?

Answer 4

an indicator used in acid-base titrations that turns red in acidic solutions and yellow in alkaline solutions.

Question 5

Describe the pH scale

Answer 5

a scale that measures the acidity - alkalinity of solutions from -14.

0-6 = acid (red)
7 = neutral (green)
8-14= alkaline (blue)

Question 6

What do acids in an aqueous solution release?

Answer 6

H+ (hydrogen) ions

Question 7

What do alkalis in an aqueous solution release?

Answer 7

-OH (hydroxide) ions

Question 8

What happens when an acid and alkali react together?

Answer 8

alkalis can neutralise acids. when they react together they form salt and water.

Question 9

What is universal indicator?

Answer 9

a mix of many indicators therefore providing a wide range of pH being able to test. it changes the colour of the solution to the colour of the pH.

Question 10

What is a standardised solution?

Answer 10

the known concentration that we use to find the unknown.

Question 11

What are the general rules for predicting solubility of ionic compounds?

Answer 11

• common sodium, potassium and ammonium compounds are soluble
• all nitrates are soluble
• common chlorides are soluble (except silver/lead (ii))
• common sulfates are soluble (except barium, calcium, lead(ii))
• common carbonates are insoluble (except sodium, potassium, calcium)
• common hydroxides are insoluble (except sodium, potassium and calcium) however calcium hydroxide is slightly soluble

Question 12

What do acids and bases do in reactions in terms of proton transfer?

Answer 12

acids donate H+ protons to bases during chemical reactions.

Question 13

Define acid

Answer 13

an acid is a substance that donates H+ ions to base during a chemical reaction at a pH below 7.

Question 14

Define base

Answer 14

a base is a substance that accepts H+ ions during a chemical reaction.

Question 15

Define alkali

Answer 15

a base that is soluble in water and produces -OH ions over the pH of 7.

Question 16

What are the acid reactionss?

Answer 16

hydrochloric acid, sulfuric acid, nitric acid

acid + base -> salt + water
acid + alkali -> salt + water
acid + metal oxide -> salt + water
acid + metal -> hydrogen + salt
acid + metal carbonate -> salt + water + carbon dioxide