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A Level Chemistry 🫧💧 > 1.2 Amount Of Substance > Flashcards

1.2 Amount Of Substance Flashcards

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1
Q

What type of elements are monatomic

A

Noble gases (all) are monatomic
He is helium
Ne is neon
Etc

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2
Q

Which elements are always found diatomic

A

H2
N2
O2
All halogens (eg. Cl2)

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3
Q

What are the formulas for phosphorus and sulfur

A

P4
S8

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4
Q

What are the formulas for metallic elements

A

They are monatomic (eg. Fe)

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5
Q

What are the formulas for the four giant covalent structures

A

C (diamond, graphite, graphene)
Si (silicon)

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6
Q

What’s the formula for methane

A

CH4

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7
Q

What’s the formula for hydrogen sulfide

A

H2S

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8
Q

What’s the formula for sulfuric acid

A

H2SO4

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9
Q

What’s the formula for phosphoric acid

A

H3PO4

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10
Q

What’s the formula for giant cov silicon dioxide

A

SiO2

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11
Q

What’s the formula for silver, zinc, hydrogen carbonate, hydride, and phosphate (5)

A

Silver (Ag +)
Zinc (Zn 2+)
Hydrogen Carbonate (HCO3 -)
Hydride (H-)
Phosphate (PO4 3-)

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12
Q

What does substance + oxygen make?

A

substance + oxygen = oxides

  1. Metal + oxygen = metal oxide
  2. Hydrogen Sulfide + Oxygen = Sulfur Dioxide + Water (H2S + 3 O2 = 2 H2O + 2 SO2)
  3. Hydrocarbon + Oxygen = Carbon Dioxide + Water (C3H8 + 5 O2 = 3 CO2 + 4 H2O)

Any Carbon or Sulfur in the reactants ALWAYS turns into a dioxide in products

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13
Q

What does metal + water make

A

mwah

metal + water = alkali (always OH) + hydrogen
2 Na + 2 H2O = 2 NaOH + H2

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14
Q

What does metal + acid make

A

mash

metal + acid = salt + hydrogen

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15
Q

What does oxide/hydroxide/carbonate + acid make

A

baws

oxide/hydroxide + acid = salt + water
carbonate + acid = salt + water + carbon dioxide

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16
Q

What’s the equation for hydrogencarbonate + acid

A

hydrogencarbonate + acid = salt + water + carbon dioxide

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17
Q

What’s the equation for ammonia + acid

A

ammonia + acid = ammonium salt
NH3 + HCl —> NH4Cl

18
Q

What’s the equation for metal carbonate + heat

A

metal carbonate = metal oxide + carbon dioxide

19
Q

How to work out limiting reagents

A

We need to work out wch reactant is in excess and wch is limiting
For example…

..
2SO2 + O2 —>2SO3

We have 5 mol of SO2, and 2 mol of O2
With 5SO2, we need 2.5O2
With 2O2, we need 4SO2

This means O2 is the limiting reagent as is causes less product to be reduced

20
Q

What’s average bond enthalpy

A

With the energy needed to break one mole of a specific bond
In a molecule in gaseous state

Usually, reactants are endothermic (take in energy to stay separated) (+number)
Products are exothermic (let out energy to stay together) (-number)
—> they energy required to break a specific bond
- has same value as energy released when that bonds formed

21
Q

How to find molecular formula from Mr of empirical formula

A

Empirical = CH2
Mr (for molecular formula) = 42

  1. Find formula mass of empirical..
    14

Mr / empirical Mr = 42/14 = 3

Molecular formula = 3 x Empirical = C3H6

22
Q

How to find empirical formula of compound
From its composition (percentage or mass)

A

Write the mass/percentage of each element

Divide each mass/percentage by Ar of element
NOT Mr

Find simplest whole number ratio of these numbers
Divide by the smallest number
Then multiply to make whole numbers

23
Q

What’s the ideal gas law 🟡

A

To do equations with gases, we treat all gases like ideal gases
(No forces between particles, particle size is insignificant etc)

Ideal gas law is used for all gases..
PV = nRT

pressure, vol (m3), number moles, gas constant, temp (k)
- R= 8.31 J mol-1 K-1
- K = °C + 273

24
Q

What does a volume of gas depend on

A

Depends on temperature, pressure and number of moles
What the gas is doesn’t affect the volume

Means under same conditions (temp and pressure)
Eg. 100cm3 of one gas contains same number of moles as 100cm3 of any other gas

25
Q

Room temperature and pressure

A

25°C and 101kPa

26
Q

Dilution calculation

A

N = CV
Moles = conc x volume (dm3)

27
Q

How to do titration calca (and base)

A

Yaaa

28
Q

How do you prepare a burette for use? Apparatus needed?

A
  • burette
  • pipette with safety filler
  • volumetric flask
  • conical flasks

To prepare..
Rinse burette with deionised water
Ensure water flows through jet, then discard water
Rinse burette with solution you’re filling with
Discard it once know it flows through
Discard solution
Charge burette with solution you’re filling with

29
Q

🚨In titrations what effect will rinsing burette with dionised water have on titre value

A
  • titre value increases
  • as solution would be more dilute, with a larger volume
30
Q

Why should you use the sample youre filling the burette with to rinse instead of water

A
  • water would dilute the sample
  • use of water will change conc
31
Q

Why does rinsing the inside if the conical flask with deionised water improve titration’s accuracy 🚨

A

Ensures all the acid/alkali on the side if the flask is rinsed off

32
Q

What’s concordance 🚨

A

Titres within 0.1cm of each other

33
Q

Whats volumetric analysis

A

How titrations are used to accurately determine concs of unknown solutions
- need to know conc of volumetric solution (wch reacts with unknown)
- need to know volumes of solutions

34
Q

Why do we need to accurately weigh out appropriate mass of solute (reweighing empty weigh boat after pouring solute into beaker)

A

It is how we calculate number of moles present in solution.
And hence then calculate conc.
- avoids overestimation of mass added
- as a result of some solid remaining in weigh boat

35
Q

Why did we break up solid with stirring rod

A

Ensures all solid dissolves
It increases SA wch speeds up dissolution

36
Q

Why did we use
- funnel to pour solution into volumetric flask
- rinse glass rod into volumetric flask
- and rinse inside beaker many times and pour washings into flasks

A

Ensures all dissolved solute ends up in volumetric flask

37
Q

Why is base of meniscus on the mark

A

Ensures accurate measure of volume of solution made
Narrow neck design of volumetric flask minimises error with formation of meniscus

38
Q

Why did we put lid in volumetric flask and invert 10 times

A

So solution is homogeneous (conc throughout solution is same)
Pipettung out aliquots (known volumes) from any part of solution wont affect conc of solution removed

39
Q

Molar mass

A

Mass(g)/mol

40
Q

Molar mass

A

Mass(g)/mol

41
Q

How to find mass of an atom / ion

A

Get atomic mass (/1000 to kg)
Then divide by avagadros

42
Q

How do you make volumetric solutions

A

Titrations are used to determine concentration of unknown solutions
—> this is volumetric analysis
— Done by preparing a volumetric solution and then carrying out
A reaction between a known volume of that and the unknown solution
– the key to determining the conc of the unknown solution
– is knowing conc of volumetric solution and measuring both solution volumes accurately

To do this..
1. Weigh appropriate masses of solute
- find mass of an empty weigh boat
- add appropriate mass of solute to the boat and reweigh
- empty solute into 250cm3 beaker
- reweigh empty weigh boat

  1. Dissolve all solute in beaker by adding
    75–100cm3 of distilled water and stir with stirring rod (break up solid)
  2. Pour solution into volumetric flask with funnel
    Rinse inside beaker and pour into flask (dont add over 250cm3)
  3. Carefully make solution up to the mark using a clean pipette
    Ensuring meniscus is on mark
  4. Place lid on volumetric flask and invert 10 times

A Level Chemistry 🫧💧 (7 decks)

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