Calculations & Chemical Equation Flashcards
What is a mole?
A unit that defines an amount of something
- I mole of atoms = 6.022 x 10^23 atoms
What is Avogadro’s number?
Basis for concept of mole (abbreviated mol)
What is atomic mass and molar mass?
Atomic mass: one atom of an element corresponds to average mass of a single atom in amu
Molar mass: one mole of an element corresponds to mass of a mole of atoms in grams
Same #, different units
How do you convert atoms, moles, and mass?
- Density converts between grams and milliliters
- atomic mass unit converts between amu and grams
- Avogadro’s number converts between moles and # of atoms
- molar mass converts between grams and moles
What are the formulas to convert between moles, particles, and grams?
- Grams to moles: divide by molar mass; g x 1 mol/g = mol
- Moles to grams: multiply by molar mass; mol x g/1mol = g
- Particles to moles: divide by avogadro’s #; particles x 1mol/(6.022 x 10^23) = mol
- Moles to particles: multiply by Avogadro’s #; x (6.022 x 10^23)/1mol = particles
What is a chemical formula?
Combination of symbols of various elements that make up the compound
What is a formula unit?
Smallest collection of atoms that provides two important pieces of information
- identity of atoms/ions
- relative # of each type of atom/ion
What is a hydrate?
Compound containing 1 or more water molecules as integral part of structure
What is a formula mass?
Sum of atomic masses of all atoms in compound as represented by formula (expressed in amu)
Ex: H2O: 16.00amu+2(1.008 amu)= 18.02 amu
What is molar mass?
Mass in grams of 1 mole of compound in grams/mole (numerically equal to formula weight in amu)
Ex: molar mass of H2O: 18.02g/mol
What are the two parts of a chemical equation?
Reactants: substances that undergo change in a reaction
Products: substances produced by reaction
What are features of a chemical equation?
- Identity of products and reactants must be specified using chemical symbols
- Reactants are written to left of reaction and products to right
- Physical states of reactants and products may be shown in parenthesis
- Symbol 🔺over reaction arrow means that energy is required for reaction to occur
- Equation must be balanced
What is physical evidence of a reaction occurring?
- Release of gas
- Formation of a solid (precipitate)
- Heat is produced /absorbed
- Color changes
What are the different types of reactions?
- combination reaction
- decomposition reaction
- single-replacement reaction
- double-replacement reaction
What is a combination reaction?
Joining of 2 or more elements/compounds, producing a product of different composition: A + B →AB
What is a decomposition reaction?
Produce 2 or more products from a single reactant: AB → A+B
What is a single-replacement reaction?
One atom replaces another in compound producing a new compound: A + BC → B + AC
What is a double-replacement reaction?
2 compounds undergo a “change of partners”: AB + CD →AD + CB
What is the law of conservation of mass?
Matter cannot be either garned or lost in process of chemical reaction: total mass of products = total mass of reactants
How do you balance an equation?
- Count #s of moles of atoms of each element on both product and reactant sides
- Determine which elements are not balanced
- Balance one element at a time by changing coefficients
- Balance any other elements
- Check
What is a precipitate?
Chemical change that results in one or more insoluble products
- to predict if precipitation reaction → know solubilities of ionic compounds
- reference notes for solubility chart *
How do you predict whether a precipitation will occur?
- Recombine ionic compounds to have them exchange partners
- any insoluble salt will be precipitate
What is an ionic equation?
Conveys how products and reactants exist in solution
- soluble ions are dissociated
- insoluble ions present as solid
What is a net ionic equation?
Spectator ions do not change and not induced
