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IB Chem HL > Chapter 1: Stoichiometry > Flashcards

Chapter 1: Stoichiometry Flashcards

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1
Q

What are elements?

A

Made up of a single type of atom.

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2
Q

What are Isotopes?

A

Atoms of an element which contain a different amount of neutrons, therefore have different physical properties.

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3
Q

What are compounds?

A

Two or more elements chemically combined in fixed ratios.

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4
Q

What is atom economy and its equation?

A

The atom economy of a reaction is its efficiency to produce a specific product.
(Mass of desired products/total mass of products) x 100

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5
Q

What are mixtures?

A

A mixture is a composition of elements/compounds in which there is no chemical combination.

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6
Q

What is the Kinetic theory of matter?

A

The average kinetic energy of particles are directly related to the temperature of a system.
KE is proportional to Temperature (Kelvin)

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7
Q

Why does diffusion only occur in fluids?

A

As particles in fluids can flow over each other in random motions, therefore can disperse evenly.

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8
Q

Why do substances with lower masses diffuse more quickly at the same temperature than those with a greater mass?

A

As the kinetic energy of particles is equal at the same temperature, regardless of the nature of the substance - there is an inverse relationship between mass and velocity (KE = 1/2mv^2), therefore the greater the mass - the less the speed of particles, thus a lower rate of diffusion.

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9
Q

What is the change of state from solid to gas?

A

Sublimination

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10
Q

What is the change of state from gas to solid?

A

Deposition

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11
Q

What is the difference between evaporation and boiling of a substance?

A

Evaporation is the change of state from liquid to gas which occurs at the surface of a liquid whereas in boiling, change of state occurs throughout.

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12
Q

When does boiling take place?

A

When vapour pressure reaches external pressure.

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13
Q

What happens to boiling water at higher altitudes?

A

At higher altitudes, lower external pressure will lower the boiling point of water as lesser temperatures will be required to transfer adequate energy to the water in order for vapour pressure to reach external pressure.

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14
Q

How do pressure cookers work?

A

A pressure cooker increases the pressure, thereby increasing the boiling point of water as greater energy must be transferred to it in order for vapour pressure to reach external pressure, allowing for food to cook faster as the water reaches higher temperatures.

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15
Q

Why does the temperature stay constant at the plateaus of the change of state graph?

A

As energy being transferred is being used to break intermolecular forces between particles in order for a change of state.

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16
Q

What is Avogadro’s constant?

A

6.02 x 10^23 is the number of particles, atoms, molecules in one mole of any substance.

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17
Q

What is relative atomic mass?

A

The weighted mass of an atom compared to 1/12 of an atom of Carbon-12.

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18
Q

What is an amu?

A

An atomic mass unit is the mass of 1/12 of a carbon atom.

19
Q

Why is Carbon-12 used as a reference point for the relative scale of masses of atoms?

A

As Carbon-12 is the most abundant isotope of Carbon and its mass can be measured accurately.

20
Q

What is the relative formula mass?

A

The sum of all relative atomic masses of atoms in a formula unit of a substance(Ionic compounds)

21
Q

What is the relative molecular mass?

A

The sum of all relative atomic masses of atoms in a formula unit of a substance(molecular covalent bonds)

22
Q

Why do mols of different substances have the same number of particles but weigh differently?

A

As atoms of different elements have different masses.

23
Q

How do you calculate the mass of one molecule?

A

Molar mass/Avogadro’s constant

24
Q

What is the empirical formula of a substance?

A

The simplest whole-number ratio of atoms in a compound whereas the molecular formula is the actual number

25
Q

How do you calculate percentage composition?

A

(Mass of an element in a compound/molar mass) x 100

26
Q

What is the Limiting reactant?

A

The reactant which limits the amount of product formed, whereas the other reactant is in excess.

27
Q

What is the equation for percentage yield?

A

(actual/experimental yield/theoretical yield) x 100

28
Q

What is the difference between homogenous and heterogenous mixtures?

A

A homogenous mixture has uniform composition & properties throughout whereas a heterogenous mixture does not.

29
Q

What is a solution?

A

A homogenous mixture of 2 or more substances, solute in a solvent.

30
Q

What units are the concentration of a solution measured in?

A

mol dm^-3 or g dm^-3

31
Q

How to calculate the parts per million of a solution of very low conc?

A

(mass of component/mass of solution) x 1,000,000
1 ppm = 1 mg of solute in 1 kg/l/dm3 of solution

32
Q

What is used to describe multiple dilutions of a solution, usually by the same factor?

A

Serial dilutions

33
Q

What comprises a standard solution?

A

Made of a primary standard with high purity (99.9%), high molar mass, low reactivity and does not change composition in contact with air.

34
Q

Why should NaOH not be used to make a primary standard solution?

A

As it is a hygroscopic substance, therefore absorbs moisture from the air.

35
Q

What is a secondary standard solution?

A

A solution that has been standardised using a primary standard solution.

36
Q

What is the Kinetic molecular theory of gases?

A

Particles in a gas follow random, straight-line motion.
There are negligible forces of attraction between particles.
Collisions between particles/container are perfectly elastic (no energy is lost)
Distance between particles is much more greater than the size of particles (negligible volume)
Kinetic energy is directly proportional to the absolute temp.

37
Q

What is Avogadro’s Law?

A

Equal volumes of all gases, when measured at the same pressure and temperature contain an equal amount of particles and vice versa.

38
Q

What is the volume of one mole of gas at standard conditions?

A

22.7 dm^3 mol^1

39
Q

What is the relationshio between pressure and volume?

A

With constant temp, any increase in pressure on a fixed mass of gas results in a decrease in volume.

40
Q

What is the relationship between volume and temperature?

A

As the volume of a gas is increased as the temperature increases, at a fixed mass.

41
Q

What is the relationship between pressure and temperature?

A

At a constant volume, any increase in pressure of a gas of a fixed mass will result in a proportional increase in its temperature

42
Q

How do real gases differ from the kinetic molecular theory of gases/ideal gas laws?

A

At high pressures, intermolecular forces between particles become significant as particles are closer together.
At lower temps as well.
The non-zero volume of particles become significant as this volume contributes to the total volume of gas.

43
Q

What kinds of gases show the most ideal behaviour?

A

Gases with a low molar mass and weak intermolecular forces

IB Chem HL (5 decks)

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