2.1 - Atoms and Reactions Flashcards by Cullain Escott

Define the term isotope

Atoms of the same element which have the same number of protons but a different number of neutrons

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Why are the reactions of isotopes the same?

Chemical reactions only involve electrons. Isotopes have the same number of electrons. Therefore, they have the same chemical reaction

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What is the relative mass and relative charge of a proton, neutron and electron

Proton

Relative mass = 1
Relative charge = 1

Neutron

Relative mass = 1
Relative charge = 0

Electron

Relative mass = 1/2000
Relative charge = -1

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What never changes? The number of neutrons, the number of protons or the number of electrons?

Number of protons

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Define relative isotopic mass

Mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

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Define relative atomic mass

The weighted mean mass of an atom relative to 1/12th of the mass of an atom of carbon-12

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How do you find the Mr of an element?

1) Multiply each relative isotopic mass by its relative isotope abundance and then add the result 2) Divide this result by the sum of the isotope abundances

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When do we use the term relative molecular mass?

When referring to simple molecules

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When do we use the term relative formula mass?

When we are referring to ionic or giant covalent molecules

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List the ions formed by Group 1 - 7 elements (excluding group 4)

Group 1 = 1+

Group 2 = 2+

Group 3 = 3+

Group 5 = 3-

Group 6 = 2-

Group 7 = 1-

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What should we do when trying to work out the formula for ionic compounds?

Balance out the charges

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Define amount of substance

INSERT EXAM Q DEFINITION HERE

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Given mass and Mr, what is the formula for moles?

n = m/Mr

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Given moles and Mr, what is the formula for mass?

m = n x Mr

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Given moles and mass, what is the formula for Mr?

Mr = m/n

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What is the formula for Number of particles?

Number of particles = n x 6.02 x 10²³

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Given Avogadro’s constant and the number of particles, what is the formula for moles?

n = number of particles / 6.02 x 10²³

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Define empirical formula

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

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How do work out the empirical formula of a compound starting from its percentage composition?

1) Divide each percentage by its Mr
2) Divide each answer by whichever answer is the smallest
3) Find the lowest whole number ratio

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How do you work out the empirical formula of a compound starting from its mass composition?

1) Divide each amount of grams by its atomic mass 2) Divide each answer by whichever answer is the smallest 3) Find the Lowest whole number ratio

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What does anhydrous mean?

Without water

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What does hydrated mean?

A crystalline compund containing water molecules

E.g. CuSO₄.5H₂O

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Define water of crystallisation

Water molecules that are combined into the crystalline structure of a hydrated compound

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How do you find the water of crystallisation of a compound?

1) Work out the anhydrous mass
2) Calculate the amount of anhydrous salt (in moles)
3) Calculate the amount of water (in moles)
4) Divide the moles of anhydrous salt and moles of water smallest value of moles
5) Find the lowest whole number ratio

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For a gas at RTP, what formula would you use to work out the volume in cm³

v = n x 24000

For a gas at RTP, what formula would you use to work out the volume in dm³

v = n x 24

Given the concentration and volume, how can you find the number of moles?

n = C x V

Given the moles and volume, how can you find the concentration?

C = n/V

Given the moles and concentration, how can you find the volume?

V = n/C

What is the ideal gas equation?

pV = nRT

What do the units stand for in the ideal gas equation?

p = Pressure (Pa) V = Volume (m³) n = moles (mol) R = The Gas Constant, 8.314 T - Temperature (K) or (ºC + 273)

How do you convert Pascals to Atmospheres?

1 atm = 101325 Pa

How do you convert Degrees Celsius to Kelvin?

+273

How do you convert dm^3 / Litres to m^3

Divide by 1000

What is the formula for percentage yield?

(Actual yield/Theoretical Yield ) x 100

Define percentage yield

A measurement of the efficiency of a reaction. It is the ratio between the actual yield and theoretical yield.

Define theoretical yield

The amount of the product that should be made if no chemicals are 'lost' in the process

Define actual yield

The amount of product actually obtained from a chemical reaction

Why will the actual yield never be 100%?

- The reaction may be at equilibrium and may not reach equilibrium - Side reactions may occur leading to the formation of by-products - The reactants may not be pure. - Some of the reactants may be left behind in the apparatus used in the experiment

What steps do you use to find percentage yield?

1) Write a balanced equation 2) Find the mole ratio 3) Find the theoretical yield 4) Calculate the percentage yield using the formula

Define atom economy

The amount of starting materials, that end up as useful products

What is the formula for atom economy?

Mr of useful products / Total Mr of reactants

What type of reaction has an atom economy of 100%?

Addition reactions

What type of reactions do not have an atom economy of 100%?

Any reaction that is not an addition reaction

Name the following acids: HCl, H2SO4, HNO3 and CH3COOH

HCl - Hydrochloric acid H2SO4 - Sulphuric acid HNO3 - Nitric acid CH3COOH - Ethanoic acid

Name the following alkalis: NH3, KOH and NaOH

NH3 - Ammonia KOH - Potassium Hydroxide NaOH - Sodium Hydroxide

Define the term acid

Proton donor

Define the term alkali

Proton acceptor

What do acids release in aq solutions?

Protons (H+)

What do alkalis release in aq solution?

Hydroxide ions (OH-)

Show the dissociation of HCl, HNO3 and H2SO4

HCl → H+ + Cl- HNO3 → H+ + NO3- H2SO4 → 2H+ + SO4 ^2- NOTE : All reactants and products should be in aq solution

Show the reaction between water and ammonia

NH3(aq) + H2O (l) → OH- + NH4+

Show the reaction between a proton and a hydroxide ion

OH- + H+ → H2O

Define the term salt

When the H+ ion(s) in an acid is replaced by metal ions

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

Salt + Hydrogen

What are the products in the reaction between an acid and a metal hydroxide?

Salt + Water

What are the products in the reaction between an acid and metal oxide?

Salt + Water

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

Salt + CO2 + Water

What is meant by a titration?

A technique used to determine the concentration of a solution

Outline the method of a titration

* Add acid to burette and record the initial volume * Measure alkali in volumetric pipette using a pipette filler and add this to a conical flask * Add a few drops of indicator * Add the acid slowly to the concial flask until there is a colour change * Record the final volume of the burette * From this, calculate the volume added

How can we make a standard solution?

- Weigh a specific mass of a ample - Add a small volume of distilled water and stir until the solid has dissolved - Transfer solution into a volumetric flask using a funnel - Rinse the breaker and funnel into the volumetric flask using distilled water so no reactants are left behind. - Add water wisely until the volume equals the white mark on the volumetric flak - Shake and invert the flask to mix the contents.

When performing titration calculations, what are the key things you must do?

- Convert volume to right unit (if necessary) - Find the mole ratio - Use stoichiometric relationships

How do you work out titration calculation answers?

1) Balance the equation and find the mole ratio 2) Find the number of moles of titrant added to reach the end point 3) Determine the amount of moles of analyte that must have been present 4) Determine the concentration of the analyte 5) Check answer and check units

All elements by them-self has an oxidation number of :

0 e.g. He

The oxidation states of any molecules adds up to :

0 e.g. MgO

The oxidation state of any ion is equal to?

The charge of that ion e.g. Mg^2+ has an oxidation state of 2+

Any group 1 element has an oxidation state of?

Any group 2 element has an oxidation state of?

Any group 3 element has an oxidation state of?

The oxidation state of Fluorine is always?

-1

The oxidation state of Hydrogen is nearly always?

+1 Except for when in Metal Hydrides e.g. NaH, where it is -1

The oxidation state of oxygen is?

Nearly always -2 Except IN F2O and peroxides

The oxidation state of chlorine is nearly always?

-1 Except when bonded to oxygen

In terms of oxidation number, what is oxidation?

An increase in oxidation number

In terms of oxidation number, what is reduction?

An decrease in oxidation number

In terms of electrons, what is oxidation?

A loss in electrons

In terms of oxidation number, what is reduction?

A gain of electrons

Nitrate formula

NO3 -

Carbonate formula

CO3 2-

Sulfate formula

SO4 2-

Hydroxide formula

OH -

Ammonium formula

NH4 +

Nitric acid formula

HNO3

Work out mass number

No. of protons + No. of neutrons

Work out relative isotopic mass

Mass of 1 atom of isotope / 1/12 mass of 1 atom of C-12

Work out relative molecular mass

Add the Ar of each atom in the molecule

What are the charges on Protons, Neutrons and Electrons?

Proton = +1, Neutron = 0, Electron= -1

What are the relative masses of Protons, Neutrons and Electrons?

Proton = 1, Neutron = 1, Electron = negligible

Isotope

Atoms of the same element with different numbers of neutrons and different masses

Relative atomic mass

The weighted mean mass of an atom of an element compared with one–twelfth of an atom of carbon–12

Nitric acid formula

HNO3

Work out mass number

No. of protons + No. of neutrons

Work out relative isotopic mass

Mass of 1 atom of isotope / 1/12 mass of 1 atom of C-12

Work out relative molecular mass

Add the Ar of each atom in the molecule

What are the charges on Protons, Neutrons and Electrons?

Proton = +1, Neutron = 0, Electron= -1

What are the relative masses of Protons, Neutrons and Electrons?

Proton = 1, Neutron = 1, Electron = negligible

Isotope

Atoms of the same element with different numbers of neutrons and different masses

Relative atomic mass

The weighted mean mass of an atom of an element compared with one–twelfth of an atom of carbon–12

Ammonium formula

NH4 +

Hydroxide formula

OH -

Sulfate formula

SO4 2-

Carbonate formula

CO3 2-

Nitrate formula

NO3 -

What is the mass number? ^AX

Total number of protons and neutrons

What are some common acids and their formulae?

Hydrochloric Acid - HCl Nitric Acid - HNO₃ Sulphuric Acid - H₂SO₄ Phosphoric Acid - H₃PO₄ Ethanoic Acid (weak) - CH₃COOH

What are some common anions?

Halide - X^- Hydroxide - OH^- Sulphate - SO₄^2- Carbonate - CO₃^2- Nitrate - NO₃^- Dichromate - Cr₂O₇^2-