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Edexcel Chemistry > Formulae, Equations And Amounts Of Substances > Flashcards

Formulae, Equations And Amounts Of Substances Flashcards

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1
Q

What’s the state symbol for amount of substance

A

N

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2
Q

What’s the unit used to measure amount of substance

A

Mole

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3
Q

What does Avogadros constant represent

A

No. of atoms per mole of a carbon-12 isotope

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4
Q

How to calculate the mass of 1 mole of an element

A

Mass of 1 mole = relative atomic mass in grams

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5
Q

How to calculate moles when mass and Mr are given

A

Mol = M/Mr

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6
Q

What’s empirical formula

A

Simplest whole number ratio of atoms of each element present in a compound

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7
Q

How to calculate empirical formula

A
  • Divide amount of each element by its molar mass
  • divide Ans by smallest value obtained
  • if there’s a decimal, divide by a suitable number to make it into a whole number
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8
Q

State Avogadros Law

A

Under same T°C and Pa, 1 mol of any gas would occupy same vol

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9
Q

How much vol does a gas occupy at room T°C and Pa

A

24 dm³

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10
Q

Define molar gas molecules

A

Vol per mole of gas molecules

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11
Q

Why do diff gas particles occupy same volume

A

They are spread out hence individual diff has no effect

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12
Q

How to calculate moles when gas vol is given

A

N = Vol dm³ / 24

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13
Q

5 ideal ways in which gases behave

A
  • continuous motion
  • no intermolecular forces experienced
  • exert Pa when they collide with each other in containers
  • no kinetic enemy is lost in collisions
  • when T°C increases, kinetic energy of gases also increase
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14
Q

Write down ideal gas equation

A

pV=nRT

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15
Q

1 atmospheric pressure is equal to how many Pa

A

1 atm = 101325 Pa

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16
Q

0° is equal to how many kelvin

A

273 K

17
Q

What does conc. of solution mean

A

Amount of solute dissolved in 1 dm³ of solvent

18
Q

How do you calc. moles when conc. and vol are given

A

Mol = mol dm¯³ x dm³

19
Q

What’s a standard solution

A

A solution of known conc.

20
Q

Method of standard solutions

A
  1. Weigh solute using weigh by diff method
  2. In a beaker dissolve solute using solvent
  3. Pour solution in a volumetric flask
  4. Rinse beaker using solution and add it to flask
  5. Add solvent to flask carefully until it reaches graduation line
  6. Mix solution thoroughly to ensure complete mixing
21
Q

What is a titration

A

To work out conc. of an acid or alkali

22
Q

Method for titration

A
  1. Have acid/ alkali in burette with a known conc.
  2. Have an alkali/ acid in conical flask with a unknown conc. but a known vol. Add few drops of indicator as well
  3. Add acid/ alkali from burette to conical flask until indicator changes colour aka end point. Add drop by drop
  4. Read how much acid/ alkali was added from burette to neutralise acid / alkali in conical flask. Read at eye level and bottom of meniscus
  5. Record results to 2 dp and repeat until you get 2 concordant results (0.1cm³ apart)
23
Q

What does concentrated and dilute mean

A

Concentrated- large amounts of solute per dm³ of solvent

Dilute- small amounts of solute per dm³ of solvent

24
Q

4 common state symbols

A

L,S, G, AQ

25
Q

Define % yield

A

Efficiency of which reactants are converted into products

26
Q

5 reasons for not obtaining 100% yield

A
  • reaction may be at equilibrium
  • reactants may be impure
  • side reaction could take place
  • reactants/ products may be left behind while transferring
  • loss of products during separation and purification
27
Q

How is percentage yield calculated

A

% yield = actual
¯¯¯¯¯¯ × 100
Theoretical

28
Q

Define atom economy

A

Proportion of desired product compared to all products formed in reaction

29
Q

How’s atom economy calculated

A

Atom economy= Mr of desired product
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ × 100
Mr of All products

30
Q

Does 100% yield mean 100% atom economy

A

No, even if all reactants are converted into products, not all products of reaction will be required products

31
Q

Which type of reaction has 100% atom economy

A

Addition reactions ( 2 or more reactants are combined to form a product)

32
Q

What does systematic error mean

A

Same error appears in each measurement

33
Q

Error of mass measurement can be reduced by using which method

A

Weighing by difference method

34
Q

Explain how to measure using weighing by difference method

A
  1. Measure mass of container
  2. Add chemical to container and weigh container
  3. Calculate mass of chemical
  4. Transfer chemical and remeasure empty container
  5. Calculate mass of chemical transferred
35
Q

Is % error higher or lower when quantity measured has been reduced

A

Higher

Edexcel Chemistry (5 decks)

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