Unit 1-Acids & Bases Topic 7 Flashcards

1
Q
  1. What does the pH of a substance tell you?
  2. What range of numbers does the pH scale span?
A
  1. How acidic or alkaline a substance is (the pH of the substance)
  2. pH scale is continuous range that stretches from below 0 to above 14.

Most common pH values occur between 0 and 14.

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2
Q

What word is used to describe chemical with a pH of

a. Less than 7
b. exactly 7
c. More than 7

A

a. Acids have a pH of less than 7.
b. Water and neutral solutions have a pH of exactly 7.
c. Alkalis have a pH more than 7.

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3
Q

What is the difference between a base and an alkali?

A

Substances that can react with acids and neutralise them to make a salt and water are called bases.

Bases that dissolve in water are called alkalis.

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4
Q

How are acids and alkalis formed?

A

An alkaline solution can be formed when a metal oxide is dissolved in water.

An acidic solution can be formed when a non-metal oxide is dissolved in water.

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5
Q

The data booklet has a table of solubilities on page 8. What type of chemicals would have no effect on pH?

A

Insoluble substances will have no effect on pH.

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6
Q

Acidic and alkaline solutions can conduct electricity because they have ions that are free to carry charge.

What ion do all acids contain?

A

Hydrogen ion

H+

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7
Q

Which acids are the following formulae representing?

i) HCl or H+ (aq)Cl-(aq)
ii) H2SO4 or 2H+(aq) SO42-(aq)
iii) HNO3 or H+(aq) NO3<span>-</span>(aq)

A

i) Hydrochloric acid
ii) Sulphuric acid
iii) Nitric acid

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8
Q

Acidic and alkaline solutions can conduct electricity because they have ions that are free to carry charge.

What ion do all alkalis contain?

A

Hydroxide ion

OH<span>-</span>

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9
Q

Which alkalis are the following formulae representing?

i) NaOH or Na+ (aq) OH-(aq)
ii) Ca(OH)2 or Ca+(aq) 2OH-(aq)
iii) LiOH or Li+(aq) OH-(aq)

A

i) Sodium hydroxide
ii) Calcium hydroxide
iii) Lithium hydroxide

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10
Q

Describe how the concentration of H+ ions and pH changes when an acid is diluted.

A

When an acid is diluted the concentration of H+ ions is decreased and the pH increases towards 7.

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11
Q

Describe how the concentration of OH- ions and pH changes when an alkali is diluted.

A

When an alkali is diluted the concentration of OH- ions is decreased and the pH decreases towards 7.

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12
Q

Water is a covalent compound. These do not conduct electricity.

Yet I was always told not to make toast in the bath.

Please explain.

A

No one likes soggy toast.

A very small proportion of water molecules will dissociate into an equal number of hydrogen and hydroxide ions.

H2O(l) ⇔ H+(aq) + OH-(aq)

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13
Q

How does the concentration of hydrogen ions (H+(aq)) compare to the concentration of hydroxide ions (OH-(aq)) in water and neutral solutions?

A

In water and neutral solutions, the concentration of hydrogen ions (H+(aq)) is equal to the concentration of hydroxide ions (OH-(aq)) .

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14
Q

How does the concentration of hydrogen ions (H+(aq)) compare to the concentration of hydroxide ions (OH-(aq)) in an alkaline solution,

A

In alkaline solutions, the concentration of hydroxide ions (OH-(aq) is greater than the hydrogen ion (H+(aq)) concentration.

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15
Q

How does the concentration of hydrogen ions (H+(aq)) compare to the concentration of hydroxide ions (OH-(aq)) in an acidic solution.

A

In acidic solutions, the concentration of hydrogen ions (H+(aq)) is greater than the hydroxide ion (OH-(aq)) concentration.

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