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GCSE Chemistry Paper 1 > Quantative Chemistry > Flashcards

Quantative Chemistry Flashcards

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1
Q

What is relative formula mass?

A

The sum of the relative atomic masses of all the atoms in the molecular formula

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2
Q

What is the formula for percentage mass of an element in a compound?

A

Percentage mass = ((Atomic mass x Number of atoms)/Relative formula mass) x 100

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3
Q

What is the percentage mass of sodium in sodium carbonate Na2CO3?

A

43%

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4
Q

How much is a mole?

A

6.02 x 10^23

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5
Q

How does the mole relate to particles in a substance?

A

One mole of any substance is the amount of that substance that contains 6.02 x 10^23 particles. This could be atoms, molecules, ions or electrons

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6
Q

Why is a mole that number?

A

One mole of atoms of any substance will have a mass in grams equal to the relative formula mass

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7
Q

What is the formula for the number of moles in a given mass?

A

Number of moles = mass(g) / Relative formula mass

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8
Q

What is the conservation of mass theory?

A

Atoms/mass cannot be created or destroyed so there are the same number and type if atoms on each side of a reaction equation

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9
Q

What does it mean if the mass of the products is larger than the mass of the reactants?

A

One of the reactants is a gas found in the air but all the products are solids, liquids or aqueous because the gas is part of the reaction

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10
Q

What does it mean if the mass of the products is smaller than the mass of the reactants?

A

One of the products is a gas and all the reactants are solids, liquids or aqueous and the gas escaped during the reaction.

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11
Q

What do the big numbers in front of the chemical formulas of the reactants and products tell you?

A

How many moles of each substance take part in the reaction

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12
Q

How do you work out a balanced symbol equation using the masses of the products and reactants?

A

-Divide each substance’s mass by its relative formula mass to find the number of moles
-Divide all of these by the smallest number of moles in the reaction
-(If there are decimals) Multiply everything out so all of the numbers are whole
-Put these numbers in front of the chemical formulas

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13
Q

What is the limiting reactant in a reaction?

A

The reactant that ends the reaction by being used all the way up. The amount of product formed is normally directly proportional to it

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14
Q

How can you use the limiting reactant and balanced equation to calculate the amount of product formed?

A

-write out the balanced equation
-work out the relative formula mass of the desired reactant and product
-find out the number of moles of the substance you know the mass of
-use the equation to work out how many moles there will be of the other substance
-use this to calculate the mass

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15
Q

What is the theorectical yield of a reaction?

A

The mass of product that you calculate (theoretical because you will never get 100% of the product)

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16
Q

At room temperature (20 degrees celsius) and room pressure (1 atm) what volume will one mole of any gas occupy?

A

24dm^3

17
Q

What is the formula for finding the volume of a known mass of any gas at room temperature (r.t.p.)?

A

Volume of gas = (Mass of gas / Relative formula mass of gas) x 24

18
Q

What is the formula for finding the concentration of a substance in a solution using mass?

A

Concentration = mass of the solute / volume of the solvent

19
Q

What is the formula to convert the units of a concentration from mol/dm^3 to g/dm^3?

A

Mass = moles x Mr

19
Q

What is the formula for finding the concentration of a substance in a solution using moles?

A

Concentration = number of moles of solute / volume of solvent

20
Q

What are the negatives of reactions with low atom economies?

A

-use up resources
-make waste materials that need disposing
-unsustainable
-not profitable

21
Q

What does the atom economy of a reaction tell you?

A

How much of the mass of the reactants is wasted when manufacturing a chemical and how much ends up as useful products. 100% atom economy means all the atoms have been turned into useful products

22
Q

What is the formula for atom economy?

A

Atom economy = (relative formula mass of desired product / relative formula mass of all reactants) x 100

23
Q

What is the yield of a reaction?

A

The amount of product that is made

23
Q

What are the factors to consider when choosing which reaction to use to make your product?

A

-atom economy
-yield
-rate of reaction
-position of equilibrium (in reversible reactions)

24
Q

What is the best way around the negatives of reactions with low atom economies?

A

Finding a use for the waste products or using an alternative reaction that still makes the product you want but also makes useful by-products instead of waste products

25
Q

What is the formula for the percentage yield of a reaction?

A

Percentage yield = (mass of product actually made / maximum theoretical mass of the product) x 100

26
Q

What are the benefits of a high percentage yield?

A

-reduced waste
-reduced cost

27
Q

What are the three most common ways for percentage yield to be decreased in a reaction?

A

-not all reactants react to make the product (reversible reactions)
-side reactions (reactants may react with gases in the air or impurities in the mixture)
-product lost during separation from the reaction mixture (e.g. during filtration)

28
Q

Why can you never get 100% yield in real life?

A

Because some product or reactant will always get lost along the way somehow

GCSE Chemistry Paper 1 (5 decks)

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