Foundations in Chemistry: Acids, Bonding Redox

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What is an acid?

substances that release H+ ions when dissolved in water. Proton donors

What is a strong acid?

an acid that fully dissociates when dissolved in water

Give 3 examples of strong acids

HCl, H2SO4, HNO3

Give an example of a weak acid

CH3COOH, ethanoic acid

What is the difference between a base and an alkali?

an alkali is a base that dissolves in water, releasing OH- ions

How can you identify a salt in a reaction?

It will be an ionic compound (metal and non-metal).

What are the products of a reaction between an acid and a metal carbonate?

salt, water and carbon dioxide

What are the common bases?

metal oxides, metal hydroxides, metal carbonates and alkalis

Give the ionic equation of a neutralisation reaction

H+ + OH- = H2O

What are titrations used for?

Finding out exactly how much acid is needed to neutralise a quantity of alkali

Give an example of an indicator used in a titration

methyl orange, phenolphthalein

What is a standard solution?

a solution of known concentration

Describe the preparation of a standard solution

1) Work out mass of substance needed to be weighed by multiplying the concentration by the volume to get the mole. Then, multiply the mole by the molar mass to get the mass.

2) Dissolve substance in a beaker with distilled water. Then, pour solution into a volumetric flask, including the rinsings from the beaker. Add distilled water until bottom of meniscus is on the graduation line

What is a meniscus?

The curved upper surface of a liquid in a tube

Describe how to carry out an acid-base titration

1) Add 25cm^3 of the solution of known concentration into a conical flask

2) Place flask on white tile and add indicator (e.g. methyl orange)

3) Add solution of unknown concentration and volume into a burette

4) Turn on tap, swirling the flask until there is a colour change signalling the end-point

5) Calculate the volume of solution added. Repeat titration until there are at least 2 concordant results

What is the process to calculate unknown concentration?

1) Write a balanced equation for the reaction

2) Calculate the amount in moles of the known solution that reacted

3) Use stoichiometry to calculate the amount in moles of the unknown solution that reacted

4) Calculate the unknown concentration by dividing the moles by the volume

How can the percentage uncertainty be calculated?

((uncertainty number of readings) / measured value ) 100

Define oxidation number

a number assigned to an element in chemical combination which represents the number of electrons lost or gained by an atom of that element in the compound

What is the rule for assigning an oxidation number to a pure element?

the oxidation number is zero

What is the rule for assigning an oxidation number to monatomic ions?

the oxidation number is equal to ionic charge

What does the sum of the oxidation numbers equal?

the overall charge of the compound (e.g. in a polyatomic ion, it equals the overall charge on the ion)

What is a redox reaction?

a chemical reaction involving both oxidation and reduction

What is oxidation?

the loss of electrons and increase in oxidation number

What is reduction?

the gain of electrons and decrease in oxidation number

Definition of an Acid

releases H+ ions

definition of an alkali

releases OH- ions

What is a base?

a substance that can accept H+ ions

A sample of magnesium contained 24Mg: 78.60%; 25 Mg: 10.11%; 26Mg: 11.29%.

Calculate the relative atomic mass of this sample of Mg.

Give your answer to four significant figures.

[2 marks]

2.

The mass spectrum of a sample of tellurium is shown in Figure 1.

Use Figure 1 to calculate the relative atomic mass of this sample of tellurium.

Give your answer to one decimal place.

what is a strong acid?

acid that completely dissociates in solution

what is a weak acid?

something that only partially dissociates in solution

What is an ion?

charged atom or molecule

Definition of an Isotope?

atoms of the same element with the same number of protons and elections but a different number of neutrons

What is ionic bonding?

it involves the transfer of electrons from a metal to a non-metal

What is a covalent bond?

strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.

What elements can form hydrogen bonds?

Nitrogen (N), Oxygen (O) and Fluorine (F)

How many electrons are in a P-subshell?

6

How many electrons can a s-subshell hold?

2

How many electrons can a d-subshell hold?

10

How many bonding pairs are in a linear bond? Name an example. What is the bond angle?

2 bonding pairs, Beryillium Chloride or Carbon Dioxide and the angle is 180 degrees

How many bonding pairs and lone pairs are in a non-linear molecule?

2 bonding pairs and 2 lone pairs

Bond angle of NON-linear molecules? And an example

104.5, H2O

Pyrimidal molecules: How many lone pairs, bonding regions, angle and an example?

1 Lone pairs

3 bonding regions

107 degree angle

Ammonia NH3

Trigonal Planar: how many bonding regions, lone pairs and what is the bond angle?

3 Bonding regions/pairs

No lone pairs

120 degrees

BF3 is an example

Octahedral molecules: How many bonding pairs?

6

What is the bond angle of an Octahedral molecule?

90 degrees

What is the bond angle in a tetrahedral molecule?

109.5 degrees

How many bonding regions does a tetrahedral molecule have?

4

Barium metal can be extracted from barium oxide, BaO, by reduction with aluminium. 6BaO + 2A/ 3Ba + Ba3Al2O6

Calculate the mass of barium metal that could be produced from reduction of 500 g of barium oxide using this method.

Nickel makes up 25% of the total mass of a fifty pence coin. A fifty pence coin has mass of 8.0 g.

(i) Calculate how many moles of nickel atoms are in a fifty pence coin.

Aqueous silver nitrate can be used as a test for halide ions. A student decided to carry out this test on a solution of magnesium chloride. The bottle of magnesium chloride that the student used showed the formula MgCl2.6H20.

The student dissolved a small amount of MgCl2.6H20 in water and added aqueous silver nitrate to the aqueous solution.

(i) What is the molar mass of MgC/2.6H20?

In gmol-1

What is produced when an acid reacts with a metal?

Salt + Hydrogen gas is produced.

What is made when a Oxide reacts with an acid?

Salt and water is produced.

What is made when a metal hydroxide reacts with an acid?

Salt and water is produced.

What is made when a carbonate reacts with an acid?

Salt, water and carbon dioxide is produced.

What is made when a hydrogen carbonate reacts with an acid?

Salt, water and carbon dioxide is produced.

What is made when an acid reacts with ammonia?

ONLY an ammonium salt is made.

Definition of relative isotopic mass

weighted mean mass of an isotope compared with 1/12th mass of carbon-12.

What are the chemical properties of an isotope?

Isotopes of an element have the same number of protons and electrons, they will react in the same way as chemicial properties are determined by electron arrangement.

What are the physical l properties of heavy and lighter isotopes?

Physical properties are determined by the mass of the atom.

Isotopes with more neutrons will be heavier, heavier isotopes have higher melting and boiling points.

Lighter isotopes are denser.

What is the name of this Ion? (NO3-)

NO3 – is a Nitrate Ion.

What is the name of this Ion? (SO4 2-)

SO4 2- is a sulphate ion.

Write down the formula and charge for a sulphate Ion

SO4 2-

Write down the formula and charge for a nitrate ion

NO3-

Write down the formula and charge for an ammonium ion

NH4+

What is the name of this ion? (NH4+)

Ammonium

What is the name of this Ion? (CO3 2-)

CO3 2- is a carbonate ion.

What is the name of this Ion? (OH-)

OH- is a Hydroxide ion

What is the name of this ion? (Zn2+)

Zinc Ion

What is the name of this ion? (Ag+)

Silver Ion

Write down the formula and charge for a silver ion

Ag +

Write down the formula and charge for a hydroxide ion

OH-

Write down the formula and charge for a carbonate ion

CO3 2-

Write down the formula and charge for a zinc ion

Zn2+

What is the value of Avagadro’s constant?

6.02 × 10^23 mol–1

What is Avagadro’s constant supposed to represent?

The number of particles per mole

Mole is the unit for what? ‘mol’

mole (symbol ‘mol’), as the unit for amount of substance

What is the molar gas volume?

molar gas volume (gas volume per mole, units dm3 mol–1)

What does it mean by ‘molar mass’?

molar mass is the mass per mole, units (g mol–1)

State the definition of the term ‘empirical formula’

The simplest whole number ratio of atoms of each element in a compound.

State the expression for the ideal gas equation. (Letters only)

pV = nRT

p stands for pressure and is measured is pascals, Pa

V stands for volume and is measured in meters cubed (m³)

n is the mols, this can be found by concentration x volume or mass/molar mass.

R is the gas constant, it is 8.314.

T is the temperature, it’s in kelvin (K)

How to convert from degrees celcius to Kelvin?

Add 273

How to convert from Kelvin to degrees celcius?

Subtract 273.

How to convert dm³ into m³

Divide by 1000

How to convert from cm³ to m³

Divide by 1,000,000 (One million)

What is the equation linking moles, concentration and volume?

moles = concentration x volume

Equation for percentage yield

Actual yield/ Theoretical yield x 100

Equation for atom economy

desired product(in question) / all products x 100

What are the benefits of a chemical processes with a high atom economy?

• Less waste

• Greater sustainability

• Reduced use of raw/finite resources

Definition of relative atomic mass

weighted mean mass of an atom of an element relative to 1/12th of an atom of Carbon-12

What does the state symbol (g) mean?

gas

What does the state symbol (l) mean?

Liquid

What does the state symbol (aq) mean?

aqueous (dissolved in water)

what does the state symbol (s) mean?

solid

Give 3 reasons why the actual yield may be lower than the theorectical yield

reaction may not have gone to completion

side reactions may have taken place

purification of the product may result in some loss of the product

What is the formula of hydrochloric acid? Is it a strong acid?

HCl is a strong acid.

What is the formula of ethanoic acid? Is it a strong acid?

CH3COOH is a weak acid.

What is the formula of nitric acid, is it a weak acid?

HNO3 is a strong acid.

What is the formula of sulphuric acid, is it a strong acid?

H2SO4 is a strong acid.

What is the formula of Sodium hydroxide, is it an alkali or a base?

NaOH is an alkali

What is the formula of potassium hydroxide, is it a base?

KOH is an alkali. (water soluble base)