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Chemistry > TOPIC 5: FORMULAE, EQUATIONS AND AMOUNTS OF SUBSTANCES > Flashcards

TOPIC 5: FORMULAE, EQUATIONS AND AMOUNTS OF SUBSTANCES Flashcards

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1
Q

What is Avogadro’s number?

A

6.02 x 10^23

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2
Q

How do i calculate number of moles given number of particles

A

Moles= Number of particles you have/Number of particles in a mole (Avogadros number)

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3
Q

Define molar mass

A

The relative molecular mass

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4
Q

Two equations for moles

A
  1. Concentration x volume

2. Mass/Mr

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5
Q

2 Equations for concentration

A
  1. Concentration=mass of substance/volume

2. Concentration=moles/volume

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6
Q

When a base reacts with an acid what does it form

A

A salt and water

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7
Q

How to calculate number of moles of a gas

A

volume in dm3/Molar gas volume

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8
Q

What is the Molar gas volume at Room temperature

A

24 dm^3mol^-1

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9
Q

Ideal Gas Equation and define each term

A

PV=nRT

P= Pressure 
V= Volume 
N= Number of moles 
R= gas constant 
T= Temepraure in Kelvin
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10
Q

What is the gas constant?

A

8.31 J k^-1

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11
Q

Describe the colour change for methyl orange

A

From an Acid to an alkali it turns from yellow to red

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12
Q

Describe the color change for phenolphthalein

A

From an Acid to an Alkali it turns from red to colourless

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13
Q

How to calculate percentage uncertainty

A

Uncertainty/Reading x 100

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14
Q

what is the uncertainty

A

Resolution/2

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15
Q

How to work out Total uncertainty of an experiment

A
  1. Find the percentage uncertainty for each bit of equipment
  2. Add the individual percentage uncertainties
  3. Take this uncertainty and take it from the result
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16
Q

Equation for percentage yield

A

actual yield/theoretical yield x 100

17
Q

Equation for atom economy

A

Atom economy = Relative formula mass of desired products / Relative formula mass of all reactants x 100

18
Q

What is the molar mass

A

The same as the relative molecular mass but instead molar mass has units gmol -1

19
Q

What is the empirical formula

A

Gives the smallest whole number of ratio of atoms of each element in a compound

20
Q

What is the molecular formula

A

Gives the actual numbers of atoms of each type of element in a molecule

21
Q

How to calculate the percentage composition of an element

A

Percentage composition of element = Total mass of element in compound/ Total mass of compound x 100

22
Q

What happens in a precipitation reaction

A

If two aqueous compounds react together and one of the products forms as a solid a precipitation reaction takes place

23
Q

How do you use the ideal gas equation to work out the molar mass of an unknown volatile liquid

A
  1. Put a known mass of the liquid in a flask then attach it to a sealed gas syringe
  2. Gently warm the apparatus in a water bath until the liquid completely evaporates
  3. Record the volume of gas in the syringe and the temperature of the water bath
  4. Use the ideal gas equation to work out the number of moles of the liquid in your sample and use the equation moles= mass/mr to find mr
24
Q

How can we reduce percentage uncertainty

A

If we use a larger volume of liquid for example percentage uncertainty will be lower

25
Q

What is a systematic error

A

They are the same every time you repeat an experiment and can be caused by an error due to the set-up

26
Q

What is a random error and how do we reduce it

A

An error that make the results a bit different when you repeat and experiment. Repeating the exepriemtn and calculating a mean will reduce the effect of random error

27
Q

What is meant by the theoretical yield

A

The mass of product that should be made in a reaction if no chemicals are lost in the process

28
Q

What is the atom economy for addition reactions

A
  1. 100 % as the reactants combine to form a single product and no atoms are wasted
29
Q

What is the atom economy and percentage yield in substitution reactions

A
  1. The atoms of the reactant are swapped and you get the desired product and the bi-product
  2. Substitution reactions have a high percentage yield and low atom economy as a bi-product is formed

Chemistry (20 decks)

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