Exam 4 Flashcards
Chapters 15-end
What is it called when atoms bond together through their electrons?
Bond formation
What are valence electrons?
Electrons in the outermost shell of an atom. These are the ones that participate in chemical bonding.
True or false: According to the older system of grouping on the periodic table, the group number equals the number of valence electrons in an atom
true
What is the electron-dot structure?
A notation showing the valence electrons surrounding the atomic symbol.
What are the three types of bonds?
ionic (metal and non-metal), metallic (two metals), and covalent (two non-metals)
What is an Ion?
an atom that has lost or gained one or more electrons
What is a cation?
an atom that has a positive charge because it has lost electrons.
What is an anion?
an atom that has a negative charge because it has gained electrons.
What are ionic compounds?
bonds formed between a metal and a non-metal, held together by the attraction between cations and anions.
True or false: Ionic compounds must have a net charge of zero
true
Give the formula and name of the ionic compound formed by each pair of elements:
K+ and Cl-
KCl - Potassium Chloride
Give the formula and name of the ionic compound formed by each pair of elements:
Mg+2 and O-2
MgO - Magnesium Oxide
Give the formula and name of the ionic compound formed by each pair of elements: Mg+2 and F-1
MgF2 - Magnesium Flouride
Give the formula and name of the ionic compound formed by each pair of elements: Na+ and S-2
Na2S - Sodium Sulfide
Describe Metallic Compound
outer electrons in metal atoms are held only weakly by the nucleus. This weak attraction allows the electrons to move about quite freely.
What are covalent Bonds?
the type of electrical attraction in which atoms are held together by their mutual attraction for shared electrons.
True or false: multiple covalent bonds are possible
True, the number of covalent bonds an atom can have equals its number of unpaired valence electrons
What are polar covalent bonds?
Bonding electrons shared unequally between two atoms. Partial charges on atoms.
Electrons within a covalent bond are shared evenly when the two atoms are the same. H:H
They may be shared unevenly when the bonded atoms are different. H :F
What are non-polar covalent bonds?
bonding electrons shared equally between two atoms. No charges on atoms.
What are ionic bonds?
Complete transfer of one or more valence electrons. Full charges on resulting ions.
True or false: Water is non-polar
false, water is VERY polar
What are the four effects of polarity in water?
- Water has an unusually high boiling point compared to other molecules of comparable size.
- Water dissolves other polar substances
- Water dissolves many ionic substances
- Water does not dissolve non-polar substances
Explain Solubility
“Like dissolves like”
Polar compounds dissolve polar (or ionic) compounds; non-polar compounds dissolve non-polar compounds.
What are the five unusual properties of water?
- High specific heat capacity
- High heat of vaporization
- Ice is less dense than liquid water
- Dissolves a wide range of polar and ionic substances
- Has a higher than expected boiling point
What is a pure substance? Give three examples
A material consisting of only one type of element or compound
Au, NaCl, H
What is a mixture?
A collection of two or more pure substances that can be separated by physical mechanics
What are the different types of mixtures? Give examples of each
Homogenous mixtures: solution and suspension
- Air, Salt Water, White gold, milk, blood, fog
Heterogeneous mixtures
- sand in water, oil and water, sand and salt, pizza
What is a solution?
A homogenous mixture consisting of ions or molecules
Define solute and solvent
solute is the substance that gets dissolved
solvent is the substance that dissolves the solute
what is concentration?
a measure of the amount of solute dissolved in solution
concentration = solute/solution
What is the difference between saturated and unsaturated?
Saturated solutions contains the maximum amount of solute while unsaturated solutions can still dissolve more solute.
What is the difference between concentrated and dilute?
Concentrated solutions has lots of solute while diluted solutions has little solute.
What is the difference between soluble and insoluble?
Soluble solutions can be dissolved in a particular solvent while insoluble solutions can’t be dissolved in a particular solvent.
Define solubility
A measure of how much solute can be dissolved in a particular solvent at a specified temerature
True or False: most solids and liquids become more soluble as temperature increases
True
True or False: most gasses become more soluble as temperature increases
False, most gasses become LESS soluble as temperature increases
One mole = __________________________
One mole = 6.022141 x 10^23 atoms
Define molarity
a measure of concentration measured in moles solute per liter of solution
molarity = moles/liters = M
What is molar mass?
the number of grams of a substance needed to provide one mole of that substance
Explain chemical reactions
during a chemical reaction, one or more new compounds are formed as a result of the rearrangement of atoms.
reactants —> products
Define the law of conservation of mass:
no atoms are gained or lost during any reaction.
Describe the difference between reactants and products in a chemical reaction.
The number of times atoms appear before the arrow should equal the number of times they appear after the arrow.
Balance the equation:
____ H2 + ____ O2 —-> ____ H2O
2H2 + 1O2 —-> 2H2O
Balance the equation:
____Zn + ____ HCl —-> ___ZnCl2 + ___ H2
1Zn + 2HCl —–> 1ZnCl2 + 1H2
Balance the equation:
____Ag + ___S8 ——> ___Ag2S
16Ag + 1S8 —-> 8Ag2S
Balance the equation, find the molar mass, and calculate the grams of each element/compound:
___Fe + ___H2O —-> ___Fe2O3 + ___H2
2Fe + 3H2O —-> 1Fe2O3 + 3H2
2 m 3m 1 m 3 m
g = 1Fe x 56g/m = 112g
g = 3 H2O x 18g/m = 54g
g = 1 Fe2O3 x 160g/m = 160g
g = 3 H2 x 2g/m = 6g
Define reaction rates
the speed at which products form from the reactants
What are reaction rates affected by? Describe each.
Concentration: increasing concentration of reactants increases the rate of the reaction
Temperature: increasing temp. increases the rate of the reaction
Catalysts: adding a catalyst increases the rate of the reaction
What is the difference between exothermic and endothermic reactions?
Exothermic reactions are chemical reactions that results in the net production of heat.
reactants —-> products + heat
Endothermic reactions are chemical reactions in which there is a net consumption of heat.
heat + reactants —–> products
What is an Acid?
a chemical that donates a hydrogen ion, H+
an acid is any substance that, when added to water, it increaases the amount of H3O+
What is a Base?
A chemical that accepts a hydrogen ion, H+
A base is any substance that, when added to water, in increases the amount of OH-.
True or False: Acids donate protons, bases accept them.
true
What is a salt?
an ionic compound formed from the reaction of an acid and a base.
True or False: Water can behave as an acid or a base.
True
Add hydronium ions and the solution is acidic.
Add hydroxide ions and the solution is basic.
What is pH?
pH is a measure of the concentration or hydronium ions.
True or False: acid rain has a pH lower than 5
true
what is the difference between acid-based reactions and oxidation-reduction reactions?
Acid-Base reactions are the transfer of protons while Oxidation-Reduction reactions are the transfer of electrons.
What is the difference between oxidation and reduction?
oxidation is the loss of an electron while reduction is the gaining of an electron.
True or False: electric currents are generated by oxidation-reduction reactions.
true
what is a dry-cell battery?
uses a paste instead of a liquid to prevent leakage
what is an alkaline battery?
contains a base instead of an acid.
What are two examples of a rechargable battery?
NiMH (Nickel Metal Hydride)
Lithium
What is corrosion?
the process whereby a metal deteriorates through oxidation-reduction reactions
what can be used to prevent corrosion?
coating the metal with zinc
what is combustion?
an oxidation-reduction reaction between a nonmetallic material, such as wood, and oxygen.
True or False: you cannot have oxidation without reduction.
true
