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Chemistry - Y10 + Y11 > Quantitive Chemistry > Flashcards

Quantitive Chemistry Flashcards

1
Q

What is the symbol of relative atomic mass?

A

Aᵣ

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2
Q

How do you work out the Aᵣ?

A
  1. Multiply Aᵣ with number of elements
  2. Add them all up
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3
Q

How do you find out the % Mass of an element in a compound?

A

% mass of an element in a compound = Aᵣ X number of atoms in that element / Mᵣ of compound X 100

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4
Q

What does the Aᵣ of an element mean?

A

the mean mass of all of the isotopes of an element.

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5
Q

Avogadro constant

A

6.02 X 10²³

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6
Q

Formula for mass (g)

A

Mass (g) = Mᵣ X Number of moles

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7
Q

What is the conservation of mass?

A

Mass is the same for the reactants and products - mass is conserved

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8
Q

Why might the mass increase?

A

One of the reactants is a gas

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9
Q

Why might the mass decrease?

A

One of the products is a gas

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10
Q

Formula for concentration

A

Concentration (gdm-3) = Mass (grams)/ Volume (dm3)

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11
Q

How many cm3 is there is dm3

A

1000

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12
Q

How would you convert 480cm3 to dm3

A

Divide by 1000 = 0.48dm3

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13
Q

Formula for volume of gas

A

Vol of gas (dm3) = 24 X Moles

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14
Q

Atom economy formula

A

Atom economy = Mr/ Mass of desired products/ Mr/Mass of all reactants X 100

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15
Q

What is atom economy?

A

Tells you how much of the mass of the reactants wasted when manufacturing a chemical

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16
Q

What does 100% atom economy mean?

A

Means all the atoms in the reactants have been turned into useful products

17
Q

What does a low atom economy mean?

A

Low mass of useful products

18
Q

Why is it important to consider atom economy?

A
  • Raw materials are expensive, if waste is produced = less profitable
  • Less sustainable - Large quantities of reactants -> small amounts of products
  • Waste products - expensive to dispose of
19
Q

Solutions to atom economy

A
  • Use a more efficient reaction
  • Find use of waste products
20
Q

Factors to find out how profitable a reaction is

A
  • % Yield
  • Cost of raw materials
  • Rate of reaction
  • Cost of maintaining the right conidtions
  • Temperature
  • Pressure
21
Q

What is percentage yield?

A

Amount of product you get from a reaction

22
Q

Difference between actual and theoretical yield?

A

Actual yield = amount we actually get
Theoretical yield = what you expect

23
Q

Reasons why we might not make as much product

A
  • Not all reactants react to make a product - reversible reactions can turn back so yield is never 100% or reaction is slow
  • Might be side reactions - can react with gases in air or impurities to form extra products
  • You lose some product when you separit it from reaction mixture
24
Q

How to calculate percentage yield

A

actual yield (g)
/
max theooretical yield
X 100

25
Q

What is concentration?

A

Shows how much solute (grams or mols) are in a certain volume of a liquid

26
Q

Titration Method

A
  1. Collect HCL in a beaker and label it
  2. Rinse burette with distilled water and then with some HCL
  3. Fill burette with the HCL beyond the 0 mark and let soolution run out until botto m of meniscus is exacltly on the 0 mark - all bubbles should be removed from the jet
  4. Collect sodium hydroxide in a beaker and label it
  5. Rinse 25cm3 pipette with distilled water and then with sodium hydroxide
  6. Use pipette and pipette filler to transfer 25cm3 of NaOH into a clean dry conical flask
  7. Add 3/4 drops of phenolphthlein indicator into the flask and swirl. Place conical flask on the white tile directly under burette
  8. Record initial burette reading in the table below ( show be 0.00cm3)
  9. Carry out a rough titration by adding the acid to the alkali in small amountd at a time.Swirl flask after every addition and continue until indicator permanently turns pink
  10. Repeat titration accurately by adding the acid drop-wise near the end point.
  11. Repeat titration until you have 2 concondant results (within 0.10cm3)
  12. Record readings in table
27
Q

How should you read the meniscus? Where is it?

A
  • It is in a burette
  • the bottom bit is where you take reading
  • must be done at eye level
  • need 3 readings that are consistent
28
Q

What happens to the conc. if you increase the mass of the solute and keep the volume the same?

A

Conc increases

29
Q

What happens to the conc is the volume of the solution increases and the mass of the solute stays the same?

A

Conc decreases

30
Q

What is phenolphthalein in acidic and alkaline solutions?

A

acidic + neutral = colourless
alkaline = pink/red

31
Q

How do you do titration calculations

A
  1. Calc number of moles of acid used
  2. use this to find number of H ions involved in reaction
  3. this is equal to number of OH ions involved inr eaction
  4. calc number of moles of alkali used
  5. calc conc of alkali

conc and mol fomrula (2)

32
Q

1 mol of any gas takes up what volume?

A

24dm3

33
Q

In a titration calculation, how would you turn moles/dm3 to g/dm3

A

multiply conc by the Mr

Chemistry - Y10 + Y11 (10 decks)

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