chapter 4 acids, bases and redox

Question 1

weak acids? (ethanoic acid)

Answer 1

Dont completely dissociate in aq solution. Represented by a reversible reaction arrow, ethanoic acid becomes an ethanoate ion

Question 2

how does sulfuric acid dissociate?

Answer 2

One hydrogen is first lost leaving a hydrogen sulfate ion. This ion then behaves as a weak acid (partial ionisation), losing the final H to leave a sulfate ion. An equilibrium arrow is used

Question 3

base?

Answer 3

Neutralises an acid to form a salt

Question 4

alkali?

Answer 4

A base that can dissolve in water to release OH ions

Question 5

strong alkali? (metal hydroxide)

Answer 5

contain OH in the chemical formula, completely dissociate in aqueous solution

Question 6

weak alkali?

Answer 6

react with water to release OH ions, reversible reaction symbol used e.g NH3

Question 7

procedural errors of standard solution?

Answer 7

filling the flask above the graduation line : less concentrated than required, must be discarded
Not inverting the flask to mix: inconsistent conc throughout (less at top)

Question 8

uses of titration?

Answer 8

Identifying unknown chemical
finding conc of solution
testing purity of a substance

Question 9

Oxidation numbers for mono atomic ions?

Answer 9

Same as the charge on the ion

Question 10

sum of oxidation numbers in a neutral compound?

Answer 10

zero. e.g in H2O, H= +1, O= -2, (2× +1)+ -2 = 0

Question 11

sum of oxidation numbers in poly atomic ion? e.g CO3^2-

Answer 11

The same as the charge of the ion

Question 12

Oxidation numbers of group 1?

Answer 12

+1 in compounds

Question 13

Oxidation numbers for group 2?

Answer 13

+2 in compounds

Question 14

Oxidation number of Florine?

Answer 14

-1 in compounds

Question 15

Oxidation number of hydrogen?

Answer 15

+1, except in metal hydrides where it is -1

Question 16

Oxidation number of oxygen?

Answer 16

-2, except in peroxides where oxygen is -1, or in OF2 when it is +2

Question 17

Oxidation number of chlorine?

Answer 17

-1, except when combined with O or F

Question 18

preparing a standard solution?

Answer 18

Weigh out required mass of solute
Dissolve solute in beaker of minimum volume off distilled water necessary + stir
Transfer solution into volumetric flask using funnel
Rinse glass rod, funnel and beaker with distilled water into the flask
Remove funnel, add distilled water using a dropping pipette until meniscus sits on graduation line
Place stopper on flask and invert several times to mix

Question 19

Recognisable bases?

Answer 19

Metal carbonates and oxides
(G1 oxides and carbonates are soluble bases)

Question 20

what is a titration?

Answer 20

A technique used to accurately measure the volume of one solution that reacts exactly with another

Question 21

oxidising agent?

Answer 21

substance that accepts electrons

Question 22

what is a salt?

Answer 22

substance in which H ions have been replaced by metal/ammonium ions