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Chemistry > Topic 1: Stoichiometry > Flashcards

Topic 1: Stoichiometry Flashcards

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1
Q

Describe combination or synthesis reactions.

A

Combination or synthesis reactions involve the combination of two or more substances to produce a single product

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2
Q

Describe decomposition reaction.

A

Decomposition reaction involves a single reactant being broken down into two or more products.

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3
Q

Describe single replacement reaction.

A

Single replacement reaction occurs when one element replaced another in a compound. E.g. redox reaction.

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4
Q

Describe double replacement reaction.

A

Double replacement reaction occurs between ions in solution to form insoluble substances and weak non-electrolytes, also called metathesis reactions. E.g. acid-base reaction

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5
Q

What is an isomer?

A

Isomers have the same chemical formula but their atoms are arranged structurally in a different way.

E.g. butane and isobutane (methylpropane)
Isobutane is used as refrigerant, replacing CFCs that were depleting the ozone layer

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6
Q

What is atom economy?

A

Atom economy is the level of efficiency of chemical reactions by comparing the molecular mass of atoms in the reactants with the molecular mass of useful compounds.
An atom economy of 100% would suggest that no atoms were wasted.

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7
Q

What is the formula for calculating the percentage of atom economy?

A

Percentage atom economy = ((molecular mass of atoms of useful products)/(molecular mass of atoms in reactants)) x 100%

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8
Q

What is Avogadro’s constant?

A

Avogadro’s constant is a fixed number of particles

6.02 x 10^23 mol^(-1)

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9
Q

What is an isotope?

A

Isotopes are atoms of the same element that have the same number of protons in the nucleus but different number of neutrons.
Isotopes of an element have different mass numbers.

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10
Q

What is a relative abundance of an isotope?

A

A relative abundance of an isotope is a measure of the percentage that occurs in a sample of the element.

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11
Q

What is relative atomic mass?

A

Relative atomic mass of an atoms is a weighted average of the atomic masses of its isotopes and their relative abundances.

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12
Q

What is a relative molecular mass?

A

Relative molecular mass or relative formula mass for a molecule or formula is determined by combining the relative atomic mass values of the individual atoms or ions.

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13
Q

What is a molar mass?

A

A molar mass is the mass of one mole of a substance.

Has a unit of grams per mole (g mol^(-1) )

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14
Q

What is a primary standard?

A

A primary standard is any substance of very high purity and large molar mass, which when dissolved in a known volume of solvent creates a primary standard solution.
Used in acid-base titrations to improve the accuracy of the final calculation.

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15
Q

What is the formula to calculate number of particles?

A

Number of particles = moles x Avogadro’s constant

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16
Q

What is the formula to calculate moles?

A

Moles - mass (g) x molar mass (g mol^(-1))

17
Q

What is an empirical formula?

A

Empirical formula of a compound is the simplest whole-number ratio of atoms or amount (in mol) of each element present in a compound.

18
Q

What is a molecular formula?

A

Molecular formula is the actual number of atoms or amount (in mol) of elements in one structural unit or one mole of the compound, respectively.
It’s a whole-number ration of the empirical formula.

19
Q

What is Avogadro’s constant?

A

6.02 x 10^23 mol^(-1)

20
Q

What is the formula to calculate the molecular formula?

A

Molecular formula = (molar mass)/(empirical formula mass)

21
Q

What is a limiting reagent?

A

Limiting reagent controls the amount of products obtained in a reaction. It will be completely consumed during the reaction.

22
Q

What are the factors that result in reduced yield of products?

A
  • loss of products from reaction vessels
  • impurity of reactants
  • changes in reaction conditions, e.g. temperature and pressure
  • reverse reactions consuming products in equilibrium systems
  • existence of side-reactions due to the presence of impurities
23
Q

What is the formula to calculate the percentage yield?

A

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

24
Q

What is the kinetic theory of gases?

A

Kinetic theory of gases is a model used to explain and predict the behaviour of gases at a microscopic level.
Based on assumptions that:
- gases are made up of very small particles, separated by large distances. Most of the volume occupied by gas is empty space
- gaseous particles are moving in straight lines, but random directions
- gaseous particles undergo elastic collisions, no loss of kinetic energy occurs
- gaseous particles exert no force of attraction on other gases.

25
Q

What is an ideal gas?

A

Gas that under conditions of standard temperature and pressure obeys the rules of the kinetic theory of gases.

26
Q

What is STP?

A

STP is standard temperature (273K) and pressure (100kPa)

27
Q

What is the molar volume of an ideal gas at STP?

A

22.7 dm^3 mol^(-1)

28
Q

What is Avogadro’s law?

A

Avogadro’s law: equal volumes of any gas measured at the same temperature and pressure contain the same number of molecules.

29
Q

What is Boyle’s law?

A

When temperature is constant, an inverse relationship exists between pressure and volume:

P inversely proportional to 1/V

Or

V1P1 = V2P2

30
Q

What is Charles’ law?

A

For a fixed mass of gas at a constant pressure, the volume of the gas is directly proportional to the absolute temperature in kelvin.

V is proportional to T

Or

V1/T1 = V2/T2

31
Q

What is the Gay-Lussac’s law?

A

At constant volume, the pressure of the gas is directly proportional to its absolute temperature.

P proportional to T

Or

p1/T1 = p2/T2

32
Q

What is the combined gas law?

A

For fixed amount of gas:

P1V1/T1) = (P2V2/T2

33
Q

What is the ideal gas equation?

A

Ideal gas equation describes the relationship between pressure, volume, temperature and the amount (in mol) of gas particles.

pV = nRT

p (Pa) —> 1 Pa = 1 J m^(-3)
V (m^3)
T (K)

R = gas constant —> 8.31 JK^(-1) mol^(-1)

34
Q

What is the gas constant (R)?

A

8.31 JK^(-1) mol^(-1)

35
Q

What is a solution?

A

A homogenous mixture of a solute that has been dissolved in a solvent.

36
Q

What is an aqueous solution?

A

Solution where the solute is dissolved in water.

37
Q

What is a molar concentration?

A

Molar concentration of a solution is the amount (in mol) of a substance dissolved in 1 dm^3 of solvent.

1 dm^3 = 1 L

38
Q

What is the formula to calculate molar concentration of a solution?

A

Concentration (c/mol dm^(-3)) = (amount of substance (n/mol)) / (volume of solution (V/dm^3))

39
Q

What is molarity?

A

Concentration in mol dm^(-3)

Chemistry (25 decks)

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