Topic 1: Stoichiometric Relationships Flashcards
What is the Atomic Theory?
- All matter is composed of atoms.
- These atoms cannot be created or destroyed, and are rearranged during chemical reactions.
- Physical and chemical properties of matter depend on the bonding and arrangement of these atoms.
Summarize the properties of a solid:
- fixed volume
- fixed shape
- cannot be compressed attractive forces between particles hold the particles in a close-packed arrangement
- particles vibrate in fixed positions
Summarize the properties of a liquid:
- fixed volume
- no fixed shape - takes the shape of the container it occupies
- cannot be compressed
- forces between particles are weaker than in solids
- particles vibrate, rotate, and translate (move around)
Summarize the properties of a gas:
- no fixed volume
- no fixed shape - expands to occupy the space available
- can be compressed
- forces between particles are taken as zero
- particles vibrate, rotate, and translate faster than in a liquid
What is the definition of temperature and what is its SI unit?
Temperature is a measure of the average kinetic energy of the atoms or molecules in the system. The SI unit for temperature is the kelvin, K.
What happens when the temperature is an absolute zero and when the temperature is greater than absolute zero on the Kelvin scale?
Absolute zero on the kelvin scale means when the temperature at which all movement particles
stops. When the temperature is greater than an absolute zero, all particles vibrate, even in solid matter.
Convert temperature from the Celsius scale to the Kelvin scale.
temperature (K) = temperature (°C) + 273.15
Liquid → Solid
Freezing
Solid → Liquid
Melting
Liquid → Gas
Vaporization
Gas → Liquid
Condensation
Gas → Solid
Deposition
Solid → Gas
Sublimation
What is matter?
Matter is any substance that occupies space and has mass.
What are two groups matter is classified into?
Mixtures and pure substances.
What is a mixture?
A mixture is a combination of two or more pure substances that retain their individual properties.
What are the two groups that mixture us classified into?
Homogeneous mixture and heterogeneous mixture.
What are homogeneous mixtures? Give and example.
The homogeneous mixture has both uniform composition and properties throughout.
Example. Salt water, metal alloys
What are heterogeneous mixtures? Give an example.
Heterogeneous mixture has non-uniform composition and varying properties.
Example. Salad dressing, paint, garden soil.
What are pure substances?
Pure substances has a definite and constant composition.
What are two groups pure substances is classified into?
Elements and compounds.
What are elements? Give an example.
Elements are made up of atoms that each have the same atomic number.
Example. Lead, Mercury.
What are compounds? Give an example.
Compounds are made up of a combination of atoms or ions in a fixed ratio and have different properties from the constituent elements.
Example. Water, carbon dioxide, sodium chloride.
What is an Ion?
An ion is a charged particle.
What is the difference between an anion and cation?
Anions are negatively charged while cations are positively charged.
What is atom economy and state its formula?
Atom economy is a measure of the desired useful products from reactants in a chemical reaction and stated as a percent.
percentage atom economy = (molecular mass of atoms of useful products / molecular mass of atoms in reactants) x 100%
Define “The Mole”.
The mole is an SI unit, symbol mol, defined as a fixed amount, n, of a substance.
What is Avogadro’s constant?
Avogadro’s number, L, is the number of units in one mole of any substance. The units being 6.02 x 10^23 mol^-1.
What are isotopes?
Isotopes are atoms of the same element hat have the same number of protons in the nucleus but differnt numbers of neutrons.
Define “Molar Mass”.
The molar mass is defined as the mass of one mole of a substance. It has the unit of grams per mole, g/mol.
* The molar mass of a substance contains Avogadro’s number of representative particles (the particles may be atoms, molecules, or ions)
Number of Particles → Moles
÷ Avogadro’s Constant, L
Moles → Number of Particles
x Avogadro’s Constant, L
Moles → Grams
x Molar mass
Grams → Moles
÷ Molar mass
What is qualitative analysis?
Qualitative analysis focuses on determining which elements are present in a compound.
What is quantitative analysis?
Quantitative analysis enables chemists to determine the relative masses of elements which allows them to work out their exact composition.
What is the Empirical Formula? Give an example.
The empirical formula of a compound is the simplest whole-number ratio of atoms or amount (in mol) of each element present in a compound.
Example. C6H12O6
What is the Molecular Formula? Give an example.
The molecular formula is the actual number of atoms or amount (in mol) of elements in one structural unit or one mol of the compound.
Example. CH2O
Given Molecular Formula → Find Percent Composition
Step 1: State molecular formula.
Step 2: State assumption.
Step 3: Determine the mass of elements.
Step 4: Determine the mass of compound.
Step 5: Determine mass percent
Given Mass Data → Find Percent Composition
Step 1: Depict reaction and state given.
Step 2: Determine mass percent.
Given Percent Composition → Find Empirical Formula
Step 1: State givens/unknowns.
Step 2: State assumptions.
Step 3: State mass of elements.
Step 4: Determine moles of elements.
Step 5: Determine mole ratio (lowest terms/whole numbers)
Step 6: State empirical formula.
Given Empirical Formula & Molar Mass of the molecular formula → Determine Molecular Formula
Step 1: State givens/unknowns.
Step 2: Determine the molar mass of empirical formula.
Step 3: Determine the “factor” that relates the molecular formula to the empirical formula.
Step 4: Determine the molecular formula by multiplying subscripts by “factor”.
What is a limiting reagent?
The limiting reagent, often the most expensive reactant, will be completely consumed during the reaction.
What is an excess reagent?
The excess reagent is the remaining reactants that are present in amounts that exceed those required to react with the limiting reagent.
What is theoretical yield?
Is the quantity of product that is “expected” or “predicted” from a certain amount of reactant(s) under ideal conditions. The calculated (predicted) value.
What is experimental yield?
Is the quantity of product that is “actual” produced in the reaction. The measured (experimental) value.
What are the factors that affect the yield of a reaction?
- Loss of products from reaction vessels
- Impurity of reactants
- Changes in reaction conditions, such as temperature and pressure
- Reverse reactions consuming products in equilibrium systems
- The existence of side-reactions due to the presence of impurities
What is the formula to calculate the percentage yield?
% yield = (experimental yield / theoretical yield) x 100%
What is the law of definite proportions?
The law of definite proportions states a compound always forms from a fixed ratio of its elements.
What is the purpose of kinetic molecular theory of glass?
It helps explain and predict the behaviour of gasses at a microscopic level.
What are the postulates or assumptions that the kinetic molecular theory (particle theory) is based on?
- Gases are made up of very small particles, separated by large distances. Most of the volume occupied by a gas is empty space.
- Gaseous particles are constantly moving in straight lines, but in random directions.
- Gaseous particles undergo elastic collisions with each other and the walls of the container. No loss of kinetic energy occurs.
- Gaseous particles exert no force of attraction on other gases.
- All matter consists of tiny particles known as atoms
- Particles of matter are constantly in motion
- Particles of matter attract each other
- Particles of matter have space between them
- As temperature increases, particles of matter move faster
- Atoms of the same element are essentially identical and atoms of different elements are different
What is ideal gas?
Ideal gas obeys the kinetic molecular theory postulates. At high temperatures and low pressure, the attractive forces between gas molecules us insignificant and particles are separated to a high degree
What is real gas?
Real gas disobeys the kinetic molecular theory postulates. At low temperature and high pressure, gas molecules move more slowly and distance between particles decreases, so the attractive forces between gas molecules becomes insignificant (can liquefy).
What is the unit and definition of pressure?
Pressure (Pa) is a physical property of a gas defined as a force exerted by a gas as its particles collide with a surface.
What is the unit and definition of temperature?
Temperature (K) is proportional to the average kinetic energy of the particles in a substance.
What is the ideal temperature and pressure
conditions of standard temperature and pressure (STP)?
= 0 °C (273 K) and 100kPa
What is the ideal temperature and pressure
conditions of standard ambient temperature and pressure (SATP)?
= 25 °C (298 K) and 100kPa
What is molar volume?
Molar volume is the space occupied by one mole of gas (L/mol).
What is the molar volume of STP?
V(m-stp) = 22.7 dm^3 * mol^-1
What is the molar volume of SATP?
V(m-satp) = 24.8 dm^3 * mol^-1
What is Avogadro’s law?
Equal volumes of any gas measured at the same temperature and pressure contain the same number of molecules.
What is the formula for Avogadro’s law?
v1/n1 = v2/n2
What is Boyle’s law?
Boyle’s law states that there is an inverse relationship between pressure and volume of a gas when temperature and moles of gas remain constant.
What is the formula for Boyle’s law?
p1v1 = p2v2
What is Charles’s law?
Chaeles’s law states that the volume of a gas is directly proportional to absolute temperature at constant pressure.
What is the formula for Charles’s law?
v1/t1 = v2/t2
What is Gay-Lussac’s law?
Gay-Lussac’s law states that the pressure of a gas is directly proportional to absolute temperature at constant volume.
What is the formula for Gay-Lussac’s law?
p1/t1 =p2/t2
What is combined gas law?
The combined gas law states that pressure and volume are inversely proportional and that both pressure and volume have a direct relationship with the temperature of a gas and the amount of gas particles.
What is the formula for combined gas law?
p1v1/t1 = p2v2/t2
What does the Maxwell-Boltzman curve show?
This graph shows the distribution of kinetic energy (speeds) of particles of a particular gas at various temperatures.
What is the mathematical equation for ideal gas law?
pV=nRT
What is the value of the universal gas constant?
8.31 J K^-1 mol^-1 → 8.31 kPa dm^3 K^-1 mol^-1
What is a solution?
Solutions are homogeneous mixtures that consists of 2 parts: the solute and the solvent. (Most solutions are aqueous, meaning that the solvent is water, and usually the solute is a solid and is found in lesser quantity than the solvent)
What does the solubility of a solute depend on?
It depends on the nature of the molecule (polar or nonpolar) and the types of inter molecular forces that exist between solute molecules.
What is a polar molecule?
A polar molecule is usually formed when the one end of the molecule is said to possess more positive charges and whereas the opposite end of the molecule has negative charges, creating an electrical pole.
What is a nonpolar molecule?
A molecule which does not have the charges present at the end due to the reason that electrons are finely distributed and those which symmetrically cancel out each other are the non- polar molecules. In a solution, a polar molecule cannot be mixed with the non-polar molecule.
Define concentration of a solution.
The quantity of solute dissolved in a volume of a solution.
Express the concentration of a solution mathematically.
concentration = quantity of solute/volume of solute , c =m/v
What is dilution?
the process of decreasing the concentration of an aqueous STOCK (STANDARD) solution.
What happens to ionic compounds in water?
Ionic lattice dissociates when partial charges of water interact with the charged ions of the solid lattice structure of the ionic solute compound.
What happens to polar molecules in water?
Inter molecular forces between solute molecules are weakened and replaced with the partial charges of water interact with the partial charges of the polar molecules. The ability of a solute to make H bonds with water increases its solubility.
What happens to nonpolar molecules in water?
Requirement is not met. (“Like dissolves like”)
State the formula for dilution.
C₁V₁ = C₂V₂
What is the formula and units when the unit of measures of quantity is mass?
c = m/v
g/dm^3
What is the formula and units when the unit of measures of quantity is moles?
c = n/v
mol/dm^3
What is the formula and units when the unit of measures of quantity is parts?
c = m(mg)/v(dm^3)
1 ppm or 1 mg/dm^3
