R2.1 - how much? the amount of chemical change Flashcards

1
Q

What is a chemical reaction?

A

Shows the ratio of products and reactants that can be written as a chemical or symbol equation.

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2
Q

What are stoichometric co-efficients?

A

Numbers in front of products and reactants that are used to balance the equations.

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3
Q

What can a mole ratio determine?

A

1) The mass or volumes of reactants and products.
2) Concentration of products and reactants in a solution.

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4
Q

What is Avogadro’s Law?

A

Equal volumes of all gases under STP contain equal number of moles.

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5
Q

What is molar volume?

A

Volume occupied by 1 mole of a gas

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6
Q

How is titration carried out?

A

1) Use a pipette to measure a known volume of one solution into a conical flask, and add universal indicator.
2) Put the other solution in a burette, which is a calibrated glass tube.
3) Open the burette to allow the solution into the conical flask and mix it.
4) Add indicator and keep mixing until there is a permanent colour change.

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7
Q

How is back titration carried out?

A

1) Known excess of one of the reactants is added to the reaction mixture.
2) Unreacted excess is determined by titration of a standard solution.
3) Subtract the unreacted amount from the original to work out the reacting amount.
- Used when the end point is hard to identify for impure substances.

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8
Q

What assumptions are made during a back titration?

A

1) All of the substance reacts with the acid.
2) Only NaHCO3 reacted with the acid.
3) Took place under standard conditions.

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9
Q

What is the equation involving mass, moles and Mr?

A

moles = mass / Mr

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10
Q

What is the equation involving mass, molar volume and volume?

A

molar volume = moles / volume

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11
Q

What is the limiting reactant?

A

Reactant that gets used up in a reaction and determines the theoretical yield of a product.

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12
Q

What is the difference between theoretical and experimental yield?

A

Theoretical yield - maximum amount of product obtained if 100% of the limiting reactant is converted into products.
Experimental yield - yield that is actually produced from a reaction.

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13
Q

How do you work out % yield?

A

% yield = (experimental yield / theoretical yield) x 100

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14
Q

What can cause EY < TY?

A
  • Side reactions
  • Decomposition of reactants or products
  • Product lost during purifying
  • Reversible chemical reaction
  • Incomplete reaction
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15
Q

Wh cause TY < EY?

A
  • Impurities in a product
  • Product not fully dried
  • Incomplete reaction
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16
Q

How do you work out atom economy?

A

Atom economy = (Mr of desired product / Mr of sum of reactants) x 100

17
Q

What is green chemistry?

A

Sustainable design of chemical products and processes that aims to minimize the use and generation of substances that are hazardous to human health and the environment.