8.2

Question 1

What is an alkali?

Answer 1

Alkalis are bases that dissolve in water to form the hydroxide ion OH-

Question 2

What types of compounds are included in alkalis?

Answer 2

Metal Oxides and Hydroxides
Ammoina
Soluble carbonates ( Na2CO3 and K2CO3) and hydrogencarbonates (NaHCO3 and KHCO3)

Question 3

with what compounds do acids react with to form salts?

Answer 3

metals, bases, and carbonates

Question 4

what is a salt?

Answer 4

Salt is an ionic compound formed when the hydrogen of an acid is replaced by a metal or another positive ion.

Question 5

what are parent acids/bases?

Answer 5

those terms are sometimes used to describe the relationship between an acid, a base, and their salt.

Question 6

Acid + reactive metal =

Answer 6

Salt + hydrogen

Question 7

In what cases will the acid + reactive metal reaction proceed?

Answer 7

only if metal is more reactive than hydrogen ( the reactivity is presented in the data booklet)

Question 8

what are spectator ions?

Answer 8

Species which do not change during a reaction and can be cancelled out.

Question 9

What are the states of compounds included in the reaction of acid + metal ?

Answer 9

All metals - solid
all acids - aqua solution
salt - solid / if possible to dissolve - aqua solution
hydrogen - gas

Question 10

Acid + base =
What is the name of this reaction?

Answer 10

salt + water
neutralization reaction

Question 11

What is a neutralization reaction?

Answer 11

Neutralization reactions occur when an acid and base react together to form a salt and water. They are exothermic.

Question 12

What is enthalpy of neutralization?

Answer 12

enthalpy change when acid and base react to form 1 mole of water

Question 13

For reactions between all strong acid and bases the enthalpy is very similar to what? and why?

Answer 13

delta H = -57 KJmol-1
because net reaction is the same - involving the formation of water to form its ions.

Question 14

What can neutralization reactions be useful for?

Answer 14

To help reduce the effect of an acid/base

Question 15

Acid + carbonate =

Answer 15

salt + water + carbon dioxide

Question 16

what is effervescence?

Answer 16

The reactions like acid + carbonate or acid + metal involve a gas being given off so they visibly produce bubbles, known as effervescence

Question 17

What is an indicator?

Answer 17

chemical detectors, giving info about a change in the environment

Question 18

What is an Acid-base indicator?

Answer 18

an indicator that changes colour reversibly according to the concentration of H+ ions in the solution

Question 19

How are indicators usually used?

Answer 19

either as aqueous solutions or absorbed onto test paper

Question 20

indicators and their colours

Answer 20

litmus - pink in acid - blue in alkali
methyl orange - red - yellow
phenophthalein - colourless - pink

Question 21

What is universal indicator?

Answer 21

mix of several indicators

Question 22

what are acid- base titrations based on?

Answer 22

neutralization reactions

Question 23

what are neutralization reactions often used for

Answer 23

to calculate the exact concetration of an acid/alkali when the other concentration is known

Question 24

the process of acid-base titration:

Answer 24

• reacting together a carefully measured volume of one of the solutions
• adding the other solution gradually
• until the equivalmnce point ( where they neutralize each other)

Question 25

what is a good indicator?

Answer 25

the one that gives a distinct or sharp colour change at the equivalence point