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Chemistry AS Level ~Sabz ❤ > Chapter 1 ~Moles And Equations > Flashcards

Chapter 1 ~Moles And Equations Flashcards

Definitions, key ideas and formula

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1
Q

Definition of relative atomic mass (Ar)

A

The relative atomic mass is the weighted average mass of naturally occurring atoms of an element on a scale where an atom of carbon - 12 has a mass of exactly 12 units.

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2
Q

Formula for relative atomic mass of element Y:

      Ar [element Y] =
A

=average mass of one atom of element Y x 12

÷by

Mass of one atom of carbon - 12

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3
Q

Definition of nucleon number

A

°The total number of neutrons and protons in the nucleus of an atom ⚛

(extra information :the number is written either on top of the element or next to the element e.g. C-14)

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4
Q

Definition of relative isotopic mass

A

°the mass of a particular isotope of an element on a scale in which an atom of the carbon-12 isotope has a mass of exactly 12 units

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5
Q

Definition of relative formula mass

A

°the mass of one formula unit of a compound measured on a scale on which an atom of carbon-12 isotope has a mass of exactly 12 units

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6
Q

Definition of relative molecular mass

A

°the mass of a molecule measure on a scale in which an atom of the carbon-12 isotope has a mass of exactly 12 units

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7
Q

The 3 steps of determining the Ar (relative atomic mass) from a mass spectra :

A
  1. Multiple each isotopic mass by its percentage abundance
  2. add all the figures together
  3. Divide by 100
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8
Q

The definition for a mole of a substance :

A

° one mole of a substance is the amount of that substance that has the same number of specific particles (atoms, molecules or ions) as there are atoms in exactly 12g of the carbon-12 isotope

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9
Q

Definition of molar mass

A

°the mass of one mole of a substance in grams

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10
Q

Definition of Avogadro constant :

A

°the number of atoms (or ions or molecules or electrons) in a mole of atoms (or ions or molecules or electrons) :it’s numerical value is 6.02 x 10^23 (Ten to the power of 23)

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11
Q

Formula of the number of moles (Mol) =

A

=Mass of substance (g)÷/

÷molar mass(g.mol^-1)

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12
Q

Formula of mass of a substance in grams =

A

= n (num moles) x M(molar mass)

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13
Q

Definition of stoichiometry

A

The mole ratio of the reactants and products in the balanced equation for a reaction

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14
Q

In order to find the mass of products formed in a chemical reaction we use 3 things,
Namely?

A
  1. The mass of the reactants
  2. The molar mass of the reactants
  3. The balanced equation
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15
Q

Formula for the stoichiometric numbers

A

=masses in the reactions ÷ by Ar values

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16
Q

Percentage composition by mass =

A

~(Ar x number of moles of a particular element in a compound)

~÷

~(molar mass of compound)

~x 100

Example : Fe2O3 calculate irons mass %
(Ar values : Fe=55.8, O=16)

(55.8 x 2) / (55.8x2)+(16x3)

Ans x 100

17
Q

Definition of empirical formula

A

°simplest whole number ratio

18
Q

Definition of molecular formula :

A

°The formula that tells you the actual numbers of each type of atom ⚛ in a molecule

19
Q

The formula for an ionic compound is always its…..

A

Empirical formula

20
Q

The empirical formula can be deduced in 2 methods :

A
  1. determining the mass of each element present in a sample of the compound
  2. From data that gives the percentage composition by mass of the elements in a compound
21
Q

What 2 things do we need to deduce the molecular formula?

A
  1. the relative formula mass of the compound

2. The empirical formula

22
Q

3 Steps of determining the molecule formula :

A
  1. Find the empirical formula mass
  2. Divide the relative molecular mass by the empirical formula mass to get the determining factor

3.multiply the number of atoms in the empirical formula by the determining factor.
Then you have the molecular formula

23
Q

Definition of state symbols

A

°a symbol used in a chemical equation that describes the state of each reactant and product

s-solid
l-liquid
g-gas
aq- aqueous solution

24
Q

Definition of spectator ions :

A

°ions present in a reaction mixture that do not take part in the reaction (are on both sides of the ionic equation)

25
Q

The 4 steps of writing an ionic equation are….

A
  1. Write down the full balance equation
  2. Write down all the ions present. NB!!! Any reactant /product with state symbols : (s), (l), (g) or is a molecule in solution e.g. Cl2 in MgCl2 forms (Mg ^2+ and 2Cl^-) so the chlorine is together.
    Does NOT split into ions
  3. cancel spectator ions
  4. write down equation omitting the spectator ions
26
Q

What is a precipitation reaction?

A

A reaction where 2 aqueous solutions react to form a solid-the precipitate

27
Q

2 steps in writing the ionic equation for a precipitate reaction :

A
  1. Write formula of the precipitate as the product

2. Write the ions that go to make up the precipitate as the reactants

28
Q

How to change cm^3 to dm^3?

A

By dividing the number of cm^3 by 1000

29
Q

Formula for concentration (mol dm^3) =

A

=number of moles(mol) ÷volume(dm^3)

=n/V

30
Q

Number of moles(mol) =

A

C x V

31
Q

Definition of titre:

A

°in a titration, the final burette reading minus the initial burette reading

32
Q

The 3 steps of calculating the solution concentration by titration :

A
  1. Calculate the moles of acid using the formula

n=m/M

  1. Us the stoichiometry of the balanced equation to calculate the moles of base
  2. Then calculate the concentration of base using the formula

c=n/v

*can be visa versa

33
Q

3 Steps of deducing the stoichiometry by titration :

A
  1. Calculate the number of moles of each reagent using the formula

n = C x V (remember in dm^3)
NB!!! if in cm^3 than ÷by 1000

  1. Deduce the simplest mole ratio
  2. write the equation
34
Q

What is a titration?

A

A (laboratory) method or technique of determining the unknown concentration of a solution by reacting it with a known concentration of a substance.

(an acid and base)

35
Q

What is the molar gas volume?

A

24dm^3

36
Q

Formula for number of moles of a gas, n (mol) =

A

= V(dm^3) ÷ 24dm^3

37
Q

Volume of a gas (dm^3) =

A

Number of moles, n (mol) x 24dm^3

38
Q

What is a molar (M)?

A

A measure of concentration, equilavent to mol.dm^-3

Chemistry AS Level ~Sabz ❤ (7 decks)

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