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Chemistry - Y10 + Y11 > Quantitive Chemistry > Flashcards

Quantitive Chemistry Flashcards

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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

Chemistry - Y10 + Y11 (9 decks)

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