Chemistry Exam - Chapters 10 and 11

Conversion from Atoms to Mass

(# of atoms) x (1 mol / 6.02 x 10^23) = mass

Mass and Mole

(# of moles) x (# of grams / 1 mol) = mass

The Mole: Measuring Matter - What is a Mole

A mole, mol, is the SI base unit used to measure the amount of a substance. A mol of anything contains 6.02 x 10^23 representative particles. Avogadro's Number

Classifying Chemical Reactions (3) Decomposition Reactions

A single compound breaks down into two or more elements or compounds EX: AB ---> A + B EX: NH4NO3(s) --> N2O(g) + 2H2O(g) EX: 2NaN3(s) ---> 2Na(s) + 3N2(g)

Classifying Chemical Reactions (1) Synthesis Reactions

1. A chemical reaction in which two or more substances react to produce a single product EX: 2Na(s) + Cl2(g) --> 2NaCl(s) 2. Two compounds can also combine to form one compound EX: CaO(s) + H2O(l) --> Ca(OH)2(s) 3. A compound and an element can also form one product EX: 2SO2(g) + O2(g) --> 2SO3(g)

Chemical Equations: 1. In water, iron(III) chloride reacts with sodium hydroxide, producing solid iron(III) hydroxide and sodium chloride 2. liquid carbon disulfide reacts with oxygen gas, producing carbon dioxide gas and sulfur dioxide gas 3. solid zinc and aqueous hydrogen sulfate react to produce hydrogen gas and aqueous zinc sulfate

1. FeCl3(aq) + 3NaOH(aq) --> Fe(OH)3(s) + 3NaCl(aq) 2. CS2(l) + 3O2(g) --> CO2(g) + 2SO2(g) 3. H2SO4(aq) + Zn(s) --> ZnSO4(aq) + h2(g)

Steps for Balancing Equations

1. Write the skeleton equation: H2(g) + Cl2(g) ---> HCl(g) 2. Count the atoms of the elements in the reactants: H2 +Cl2 (2&2) 3. Count the atoms of the elements in the products: HCl (1&1) 4. Change the coefficients to make the number of atoms of each element equal on both sides of the equation: H2 + Cl2 --> 2HCl 5. Write the coefficients in their lowest possible ratio (smallest possible whole numbers 6. Check your work

Reactions in Aqueous Solutions (3) Reactions that form Water

Another types of double replacement. Water molecules produced increase number of solvent particles

Reactions in Aqueous Solutions (2) Precipitates

Complete Ionic Equation: equation that shows all of the particles in a solution as they realistically exist Spectator Ions: Ions that do not participate in a reaction Net Ionic Equations: equations that include only the particles that participate in the reactions. They are written from complete ionic equations by crossing out all spectator ions Double Replacements

Converting Particles to Moles

Conversion Factor = 6.02 x 10^23 representative Particles/ 1 mol ( # of representative particles) x (1 mol / 6.02 x 10^23 representative particles) = # of moles

Converting Moles to Particles

Conversion Factor = 6.02 x 10^23 representative Particles/ 1 mol (# of moles ) x (6.02 x 10^23 representative Particles/ 1 mol) = # of representative particles

Skeleton Equation btwn Carbon and Sulfur

C(s) + S(s) ----> CS2(l) (Carbon diosulfide)

Converting Mass of a Compound to Number of Particles

Determine the molar mass: (number of moles) x (molar mass) = # of grams Mult. by inverse of molar mass as conversion factor to convert mass to moles: (mass) x (1 mol / molar mass) = moles Mult. by Avogadro's Number t calc. # of formula units moles x 6.02 x 10^23 / 1 mol = formula units Calculate number of ions using ratios from chemical formula as conversion factor Calculate mass in grams of one formula unit of coumpund. Start with Molar Mass and use inverse of Avogadro's number as a conversion factor

Converting Mass of a Compound to Moles

Determine the molar mass: (number of moles) x (molar mass) = # of grams Use the inverse of molar mass as conversion factor: (mass) x (1 mol / molar mass) = moles

Converting Moles of a Compound to Mass

Calculate Molar mass: (number of moles) x (molar mass) = # of grams Covert mol to Mass by using molar mass as a conversion factor: (moles) x (# of grams / 1 mol) = mass

Reactions in Aqueous Solutions (1) Aqueous Solutions

Is a solution in which the solvent is water Create Double Replacements

Formula for a Hydrate

Problem #1: A 15.67 g sample of a hydrate of magnesium carbonate was heated, without decomposing the carbonate, to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate? Solution: 1) Determine mass of water driven off: 15.67 minus 7.58 = 8.09 g of water 2) Determine moles of MgCO3 and water: MgCO3 ⇒ 7.58 g / 84.313 g/mol = 0.0899 mol H2O ⇒ 8.09 g / 18.015 g/mol = 0.449 mol 3) Find a whole number molar ratio: MgCO3 ⇒ 0.0899 mol / 0.0899 mol = 1 H2O ⇒ 0.449 mol / 0.0899 mol = 5 MgCO3 · 5H2O

Reactions in Aqueous Solutions (4) Reactions that form Gases

This reaction occurs when you mix vinegar and baking soda

Write Chemical Equations and Classify: 1. the solid aluminum and sulfur react to produce aluminum sulfide. 2. Water and dinitrogen pentoxide gas react to produce aqueous hydrogen nitrate. 3. The gases nitrogen dioxide and oxygen react to produce dinitrogen pentoxide gas. 4. Ethane gas(C2H6) burns in air, producing carbon dioxide gas and water vapor.

(1) 2Al(s) + S(s) ------> 3Al2S3(s) Type of reaction: Synthesis Reaction (or combination reaction). (2) N2O5(g) + H2O(l) -----> 2HNO3(aq) Type of reaction: Synthesis Reaction (or combination reaction). (3) 4NO2(g) + O2(g) ------> 2N2O5(g) Type of reaction: Synthesis Reaction (or combination reaction). Since the reaction involves the combination with oxygen, it can be also considered as "combustion reaction" (4) 2C2H6(g) + 7O2(g) -------> 4CO2(g) + 6H2O(g) Type of reaction: Combustion Reaction

Percent Composition

(mass of element / mass of compound) x 100 = percent by mass (Mass of element in 1 mol compound / nolar mass of compound) x 100 = percent by mass element

Conversion from Mass to Atoms

(mass) x (1 mol / molar mass) = moles

Chemical Formulas and the Mole: Molar Mass of Compounds

(number of moles) x (molar mass) = number of grams This is done for each element and then they are added together

Symbols Used in Equations

(s) - solid, (aq) - aqueous/water solution, (l) - liquid, (g) - gas

Predict if these single displacement reactions occur: 1. 2 K(s) + ZnCl2(aq)---> 2. Cl2(g) + 2 HF(aq) --> 3. Fe(s) + Na3PO4(aq) >

1. 2 K(s) + ZnCl2(aq) ---> Zn(s) + 2KCl(aq) 2. F2 > Cl2 > Br2 > I2 Shows F2 is more active than Cl2, Cl2 cannot replace F. Cl2 + HF(aq) ------> No reaction 3. Like potassium, sodium is also one of the active metals (alkali metal - Group IA), therefore iron (Fe) cannot replace Na. Fe(s) + Na3PO4(aq) -----> No reaction

Classifying Chemical Reactions (5) Replacement Reactions

Double Displacement Reactions: exchange of ions between two compounds EX: AX + BY --> AY + BX (where A & B are cations and X & Y are anions) EX: KCN(aq) + HBr(aq) --> KBr(aq) + HCN(g)

Balancing Chemical Equations (1) : Iron and Chlorine

Fe(s) + Cl2(g) ----> FeCl3(s) 2Fe(s) + 3Cl2(g) ----> 2FeCl3(s)

The Charges of Elements - Related to Valence Electrons

For instance, those elements belonging to group 1A have only one valence electron and their charge is +1. group 2A- 2 valence electrons, charge is +2. group 3A - 3 valence electrons, charge is +3. group 4A - 4 valence electrons, charge can be +2 or +4. It depends. group 5A - 5 valence electrons, charge is -3. group 6A - 6 valence electrons, charge is -2. group 7A - 7 valence electrons, charge is -1. group 8A - 8 valence electrons, complete octet Remember that atoms gain or lose electrons in order to form a complete octet (8) of electrons.

Empirical Formula

Formula with the smallest whole number mole ratio of the elements 1. Find the percent composition ( its 100 if not given) 2. Convert to grams 3. Convert to moles 4. Using lowest mole number divide all moles (mass) x (1 mol / molar mass) =( mole / smallest element mole) = subscript

Reactivity Series: Most Reactive to Least Reactive

Metals: Lithium Rubidium Potassium Calcium Sodium Magnesium Aluminum Manganese Zinc Iron Nickel Tin Lead Copper Silver Platinum Gold Halogens: Fluorine Chlorine Bromine Iodine

Classifying Chemical Reactions (2) Combustion Reactions

Oxygen combines with a substance and releases energy in the form of light and heat EX: 2H2(g) + O2(g) --> 2H2O(g) EX: C(s) + O2(g) --> CO2(g) EX: CH4(g) + 2O2(g) --> CO2(g) + 2H2O(g)

Classifying Chemical Reactions (4) Replacement Reactions

Single Displacement: Atoms of One Element Replace atoms of another element in a compound 1. A metal replaces another metal in a compound dissolved in water depending on reactivity of metals 2. A nonmetal replaces a nonmetal in a compound 3. A metal replaces hydrogen ( lithium and hydrogen) EX: A + BX --> AX + B EX: 2Li(s) + 2H2O(l) --> 2LiOH(aq) + H2(g)

Molecular Formula:

Specifies actual number of atoms of each element in one molecule or formula unit of a substance 0. Determine molar mass of compound with empirical formula (experimentally determine molar mass / mass of chemical formula=) 1. Convert mass to moles by mult. conversion factor that relates moles to mass based on molar mass: (mass x 1mol/molar mass)=moles 2.Calculate simplest ratio among elements by diving each by smallest value in mole ratio 3. Get rid of any fractions 4. Calculate empirical formula mass using molar mass of elements 5. (experimentally determine molar mass / mass of chemical formula= # ) 6. Mult subscripts in empirical formula by that number to determine actual subscripts in molecular formula

Skeleton Equation: Potassium Chlorate(s) ---> potassium chloride(s) + oxygen(g)

Write it Out 2)K(Clo3) (s)------> KCl (s)+ O2

Skeleton Equation: Carbon Monoxide(g) + oxygen (g) ---> Carbon Dioxide(g)

Write it Out 2CO + O2 ----> 2CO2

Skeleton Equation: hydrogen(g) + bromine(g)---> hydrogen bromide(g)

Write it Out H2 + Br2 ----> 2HBr and 1) Co (g)+ O2 (g)-----> HBr

Representing Chemical Equations (3) Skeleton Equations

iron(s) + chlorine(g) ----> iron(III) chloride(s) Fe(s) + Cl2(g) ----> FeCl3(s)

Representing Chemical Equations (2) Word Equations

reactant 1 + reactant 2 ----> product 1 iron(s) + chlorine(g) ----> iron(III) chloride(s)

Representing Chemical Equations (1)

reactant 1 + reactant 2 ----> product 1 + product 2