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chemistry ocr alevel > Acids > Flashcards

Acids Flashcards

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1
Q

acids
key features

A

are sour
contain h+ ions
aqueous solution has a ph less than 7

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2
Q

Bases
key features

A

opposite of acids
aqueous solution has ph > 7.0

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3
Q

acids definition
equation
examples

A

acids dissociate in water
HX- H+ + X-
releases H+ ions into the solution
is a proton donor
HCL
HNO3
H2S04
CH3C00H

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4
Q

Alkali
definition
equation
examples

A

aqueous base
alkalis dissocate in water releasing OH- ions in the solution
X0H—- x+ OH-

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5
Q

common acids and their strengths

A

HCL- hydrochloric acid STRONG
HN03 - nitric acid STRONG
H2SO4 -sulphuric acid STRONG
CH3C00H - ethanoic acid WEAK

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6
Q

common bases and their strengths

A

Na0H - sodium hydroxide STRONG BASE (soluble)
KOH- potassium hydroxide STRONG BASE(soluble)
NH3 - ammonia WEAK BASE(soluble)

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7
Q

Ammonia as a base

A

Ammonia will dissolve in water forming a weakly alkaline solution
NH3+ + H2O (reversible equation sign) NH4+ OH-
weak base

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8
Q

definition of strength

A

measure of tendency to dissociate

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9
Q

strong acids and bases

A

fully dissociate in water
easily giving up protons or hydroxide ions

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10
Q

weak acids or bases

A

partially dissociate do not easily give up protons or hydroxide ions

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11
Q

definition of ph

A

measure of acidity or alkalinity

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12
Q

PH= -log(H+)

A

-log (H+)

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13
Q

Exam question- which of the below is a weak acid
A HCL
B H2SO4
C HNO3
D CH3COOH

A

answer= D ethanoic acid is a weak acid, it partially dissociates in water does not give up protons easily

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14
Q

Exam question= acids can be described as strong or weak. give a definition, example and equation to describe each.
a) strong

A

Strong acids fully dissociate in water releasing H+ ions in the solution
they give up protons easily, they are proton donors
example of a strong acid is HCL hydrochloric acid
equation =
XH—- X- + H+
(XH) acid

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15
Q

Exam Question= acids can be described as strong or weak. give a definition, example and equation to describe each
b) weak

A

Weak acids only partially dissociate in water releasing H+ ions in the solution. they do not give up protons easily
example= CH3C00H ethanoic acid
equation= XH ( reversible equation symbole) X- + H+
the reversible equation symbol represents partial dissociation.

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16
Q

are acids proton donors or acceptors

A

acids are proton donors, they donate H+ ions.

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16
Q

are acids proton donors or acceptors

A

acids are proton donors, they donate H+ ions.

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16
Q

are acids proton donors or acceptors

A

acids are proton donors, they donate H+ ions.

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17
Q

are bases proton acceptors or proton donors

A

bases are proton acceptors, they accept H+ ions

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18
Q

what are alkalis ( definition)

A

alkalis are aqueous bases that can dissolve in water

19
Q

give examples of what bases can include

A

,metal oxides
metal hydroxides
metal carbonates
ammonia
they neutralise acids to form salts

20
Q

Acids dissociate in water
equation
acids are proton donors that release H+ ions in aqueous solution

A

HX —– H+ + X-

21
Q

name some common acids

A

hcl - hydrochloride STRONG
h2s04- sulphuric acid STRONG
hNO3 - nitric acid STRONG
CH3C00H - ethanoic acid WEAK

22
Q

Alkalis also dissociate in water
give the equation
Alkalis are proton acceptors that release OH- ions in aqueous solution

A

XOH——– X+ + OH-

23
Q

Name some common alkalis

A

KOH- potassium hydroxide STRONG
NaOH- sodium hydroxide STRONG
NH3- ammonia WEAK

24
Q

we write H+ ions for simplicity however they are actually never found by themselves in an aqueous solution- they are always combined with H20 to form H3O+ hydroxonium ions

A

never found by themselves in aqueous solution
always combined with H2O to form H3O+ hydroxonium ions

25
Q

strength of acid or base definition

A

measure of tendency to dissociate

26
Q

strong acids will:

A

fully dissociate in aqueous solution as protons are lost easily ( donated)
e.g
HCL (aq) —– H+ + CL-

27
Q

strong bases will

A

strong bases will fully dissociate in aqueous solution as hydroxide ions are easily lost
e.g
NaOH ( aq) —— Na+ + OH-

28
Q

weak acids will:

A

weak acids will partially dissociate in aqueous solution and protons are not easily lost
e.g ethanoic acid
CH3C00H (reversible equation sign) CH3C00+ H+

29
Q

weak bases will:

A

weak bases will partially dissociate as hydroxide ions are not easily lost
e.g ammonia
NH3 ( aq) + H2O ( aq) (reversible equation sign) NH4+ + 0H-

30
Q

The reactions with strong acids and strong bases are also reversible however

A

the position of equilibrium is so far right that it can be replaced with a forward arrow as the amount the backwards reaction occurs at is negligible.

31
Q

acid base titrations
titrations are a form of volumetric analysis where a known volume of solution and a known concentration is reacted with a measured volume of a different solution
this method can be used to find chemical unknowns such as:

A

-concentration
-molar mass
-water of crystalisation
- chemical formula

32
Q

what is the end point

A

the solution in the conical flask becomes neutral at the end point

33
Q

Titration method:

A

1) a measured volume of x is added to a conical flask using a pipette along with a suitable indicator such as phenolpthalein or methyl orange.
2) the burette is filled with the other solution y which has a known concentration.
3) the tap can be opened and a small quantity of y is released into conical flask. this is allowed to occur until the end point is reached, indicated by a colour change.
4) the volume of y that was added is measured and unknowns can then be calculated.

34
Q

what are standard solutions

A

standard solutions are solutions of a known concentration. one of the solutions used in a titration must be a standard solution in order to calculate unknowns.

35
Q

method to prepare a standard solution

A

1) carefully weigh out the required mass of solute
2) dissolve solute in chosen solvent in the beaker
3) transfer the solution to a volumetric flask. rinse the beaker with initial solvent and add washings to the flask
4) add more solvent into the volumetric flask until the level is nearly at the graduation line and not on the graduation line
5) add solvent drop by drop until the bottom of the meniscus sits on the graduation line
6) seal the volumetric flask and mix it thoroughly by inverting it multiple times ensuring that the stopper is on tightly

36
Q

neutralisation occurs when?

A

an acid and a base react forming a salt and water
the general neutralisation reaction is
acid+ base—- salt + water

37
Q

the ionic equation for a neutralisation reaction is

A

H+ + OH- —— H2O

38
Q

salts are ionic compounds in which the H+ ion of an acid has been replaced with a metal ion or another positive ion

A

salts are ionic compounds in which the H+ ion of an acid has been replaced with a metal ion or another positive ion

39
Q

salts are made up of a cation and an anion:

A

cation- positive ion, usually a metal ion or ammonium ion
anion- negative ion usually derived from an acid

40
Q

example of a salt Na2SO4
cation:
anion:

A

cation - Na+
anion- so4 2-

41
Q

acid + base=

A

salt plus water

42
Q

metal + acid

A

salt + hydrogen gas

43
Q

acid + metal oxide

A

salt + water

44
Q

acid + metal carbonates

A

salt + water + carbon dioxide

45
Q

acidic salts
are formed from

A

polyprotic acids( dissociate more than once, or donate more than one proton)

46
Q

acidic salts can behave like acids
true or false

A

true- acidic salts can behave like acids

47
Q

ammonium salts
give general equation for reaction

A

are formed when acids are neautralised by aqueous ammonia
HX+ NH3—— NH4X
example- ammonia reacts with nitric acid to produce ammonium nitrate
Nh3 (aq) + HNO3—- NH4NO3 (aq)

chemistry ocr alevel (1 decks)

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