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Key Concepts In Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

1
Q

What does the pH scale measure?

A

The pH scale measures how acidic or alkaline a solution is.

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2
Q

What is the pH of a neutral substance?

A

7

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3
Q

What characterizes an acid in terms of pH?

A

An acid has a pH of less than 7 and forms H+ ions in water.

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4
Q

How does the concentration of hydrogen ions affect pH?

A

As the concentration of hydrogen ions increases, the pH decreases.

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5
Q

Define a base.

A

A base is a substance that reacts with an acid to produce a salt and water.

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6
Q

What is an alkali?

A

An alkali is a base that is soluble in water and has a pH of more than 7.

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7
Q

What ions do alkalis form in water?

A

OH- ions (hydroxide ions)

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8
Q

How does the concentration of OH- ions affect pH?

A

In alkaline solutions, the higher the concentration of OH- ions, the higher the pH.

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9
Q

What is an indicator?

A

An indicator is a dye that changes colour depending on whether it’s above or below a certain pH.

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10
Q

How do you use an indicator to measure pH?

A

Add a few drops to the solution and compare the colour to a pH chart.

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11
Q

What colour does litmus turn in acidic solutions?

A

Red

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12
Q

What is the colour of methyl orange in acidic, neutral and alkaline solutions?

A

Yellow in alkaline and colourless in acidic or neutral solutions

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13
Q

What colour does phenolphthalein turn in alkaline solutions?

A

Pink

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14
Q

What is neutralisation?

A

The reaction between an acid and a base that produces a salt and water.

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15
Q

What is the general equation for the neutralisation of hydrochloric acid with sodium hydroxide?

A

HCl + NaOH -> NaCl + H2O

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16
Q

What do the products of a neutralisation reaction have in terms of pH?

A

They have a pH of 7.

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17
Q

What is the ionic equation for neutralisation?

A

H+ (aq) + OH- (aq) -> H2O

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18
Q

What happens when an acid neutralises a base?

A

The products are neutral with equal concentrations of hydrogen and hydroxide ions.

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19
Q

What is the first step in investigating the neutralisation reaction with calcium oxide?

A

Measure out a set volume of dilute hydrochloric acid into a conical flask.

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20
Q

What equipment can be used to measure the mass of calcium oxide?

A

A mass balance.

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21
Q

What indicates that all the acid has reacted in the neutralisation experiment?

A

Unreacted calcium oxide sitting at the bottom of the flask.

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22
Q

How can you monitor changes in pH during the reaction?

A

Using a pH probe or Universal indicator paper.

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23
Q

What interesting fact is mentioned about skin pH?

A

Your skin is slightly acidic with a pH of 5.5.

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24
Q

Fill in the blank: An acid forms _______ ions in water.

A

H+

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25
Fill in the blank: An alkali has a pH of _______ than 7.
more
26
True or False: A neutralisation reaction produces a salt and a base.
False
27
What do acids produce in water?
Hydrogen ions (H+) ## Footnote Acids ionize in solution to produce H+ and another ion
28
What is the difference between strong acids and weak acids?
Strong acids fully ionize in water; weak acids do not fully ionize ## Footnote Strong acids have low pH values, while weak acids have higher pH values
29
Give an example of a strong acid and its ionization reaction.
HCl > H+ + Cl- ## Footnote Strong acids completely dissociate in solution
30
Give an example of a weak acid and its ionization reaction.
CH3COOH ⇌ H+ + CH3COO- ## Footnote Weak acids establish an equilibrium with undissociated molecules
31
What does acid strength indicate?
The proportion of acid molecules that ionize in water ## Footnote Strong acids ionize completely, while weak acids only partially ionize
32
What does acid concentration measure?
The amount of acid in a liter of water ## Footnote Concentration is different from strength; it indicates dilution levels
33
What is a concentrated acid?
An acid with a large number of acid molecules compared to the volume of water ## Footnote Dilute acids have fewer acid molecules per volume of water
34
How is concentration measured?
In grams per liter (g/L) or moles per liter (mol/dm³) ## Footnote Concentration reflects the total dissolved acid molecules
35
How does changing the concentration of an acid affect its pH?
Increasing H+ concentration by a factor of 10 decreases pH by 1 ## Footnote A factor of 100 decrease in pH by 2, and so on
36
If the H+ concentration increases from 0.001 mol/dm³ to 0.01 mol/dm³, what happens to the pH?
The pH decreases by 1 ## Footnote The new pH would be 3
37
True or False: Strong acids release all their H+ ions immediately.
True ## Footnote Strong acids dissociate completely in water
38
Fill in the blank: A solution with a hydrogen ion concentration of 0.001 mol/dm³ has a pH of _____.
4 ## Footnote This illustrates how pH is related to hydrogen ion concentration
39
What is the pH range of strong acids?
pH 0-2
40
What is produced when acids react with bases?
Salts and water
41
What is a salt in the context of acid-base reactions?
A formed compound in a neutralisation reaction
42
Salts are classified as what type of compounds?
Ionic compounds
43
What does hydrochloric acid produce when it reacts?
Chloride salts
44
What does sulfuric acid produce when it reacts?
Sulfate salts
45
What does nitric acid produce when it reacts?
Nitrate salts
46
Fill in the blank: Acid + Metal Oxide -> ______ + Water
Salt
47
What is the product of the reaction: 2HCl + CuO?
CuCl2 + H2O
48
What is the product of the reaction: H2SO4 + ZnO?
ZnSO4 + H2O
49
What is the product of the reaction: 2HNO3 + MgO?
Mg(NO3)2 + H2O
50
Acid + Metal Hydroxide -> ______ + Water
Salt
51
What is the product of the reaction: HCl + NaOH?
NaCl + H2O
52
What is the product of the reaction: H2SO4 + Zn(OH)2?
ZnSO4 + 2H2O
53
What is the product of the reaction: HNO3 + KOH?
KNO3 + H2O
54
What happens when an acid reacts with a metal?
Salt and hydrogen are produced
55
What is the product of the reaction: 2HCl + Mg?
MgCl2 + H2
56
What is the product of the reaction: H2SO4 + Mg?
MgSO4 + H2
57
What is produced when an acid reacts with a metal carbonate?
Salt, water, and carbon dioxide
58
Fill in the blank: Acid + Metal Carbonate -> ______ + Water + Carbon Dioxide
Salt
59
What is the product of the reaction: 2HCl + Na2CO3?
2NaCl + H2O + CO2
60
What is the test for hydrogen gas?
Using a lighted splint that produces a 'squeaky pop'
61
How do you test for oxygen?
A glowing splint applied to a sample of oxygen gas will relight.
62
How can you test for carbon dioxide?
Bubbling it through limewater
63
What happens to limewater when carbon dioxide is present?
It turns cloudy
64
What do nitrates produce when they react?
Nitrate salts
65
Write a balanced chemical equation for the reaction of hydrochloric acid with calcium carbonate.
2HCl + CaCO3 -> CaCl2 + H2O + CO2

Key Concepts In Chemistry (28 decks)

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