Chem test 2 with HW questions
Percent yield:
% yield = (actual yield / theoretical yield) x 100%
Percent Composition of Compounds: -The following formula allows us to calculate for the percent composition knowing the formula:
%element = (mass element/ total mass compound) X 100
nonelectrolyte are
(NH2)2CO (urea), CH3OH (methanol), C2H5OH (ethanol), C6H123O6 (glucose), and C12H22O11 (sucrose)
The oxidation number of Fe in K3Fe(CN)6 is
+3
The oxidation number of N in NaNO3 is
+5
For the chlorate ion, ClO3- , what are the oxidation states of the Cl and O, respectively?
+5,-2
The oxidation number of S in K2SO4 is
+6
-Base: A base will be defined as any substance that produces hydroxide ion or proton acceptor. Ex: Sodium hydroxide is an ionic compound containing metal ion (........) and anion, ........... Sodium hydroxide is a base b/c ........................... NaOH (aq) .........(aq) + .............(aq)
- Na+, OH-, OH- -OH-, Na+
The oxidation number of N in N2H4 is
-2
-If 2.0 moles HCl is dissolved in water, the solution produces .......... moles of H+ and ........... moles of Cl-. -How many strong acids are there? .................. -Do we need to know them by heart? ................
-2.0, 2.0 -7 - yes
A mole of a substance contains Avogadro's number of molecules (or formula units).
-A dozen eggs = 12 eggs -A mole of H = 6.02 x 1023 atoms of H
Gravimetric Analysis:
-An analytical technique base on the measurement of mass. -The procedure provides an accurate measurement.
d.Disproportionation Rxn:
-An element in one oxidation state is simultaneously oxidized and reduced.
3. Oxidation-Reduction Reactions:
-Another type of reaction in water is oxidation-reduction (redox). -There is an electron exchange between two reactants. -One species loses electrons and is said to be oxidized. -The other species gains the electrons and is said to be reduced.
Bronsted Acids and Bases: Arrhenius definitions of acids and bases are limited to that in water. Broader definitions were defined by Bronsted.
-Bronsted acid is a proton donor (gives away H+). -Bronsted base is a proton acceptor (accepts H+).
Problem 5: a. Write the chemical formula for calcium carbonate, b. Calculate the number of moles present in 10.6 g of calcium carbonate.
-CaCO3 -0.106 moles
Acid-Base reactions Leading to Gas Formation:
-Certain salts like carbonates (containing CO3 2- ions), bicarbonates (containing HCO3 - ion), sulfites (containing SO3 2- ion), and sulfides (containing S 2- ions) react with acids to form gaseous products.
Strong bases vs. weak bases: -A strong base in water is ionized completely to form ...................... and .............. -How many strong bases are there? .............. lithium hydroxide sodium hydroxide potassium hydroxide calcium hydroxide strontium hydroxide barium hydroxide -These bases in water are ......................... electrolytes.
-OH-, cation -6 -strong
-Oxidation and reduction occur together. -The species that is reduced is called an ...................... agent. -The species that is oxidized is called a ...................... agent. -The term oxidation rxn refers to the half-rxn that involves loss of electron(s). -A reduction is a half-rxn that involves gain of electron(s). COMMON SENSE: -The number of electrons loss must be equal to the number of electrons gained.
-Oxidizing agent -reducing agent
e. Combustion Reactions:
-Reaction with oxygen gas; this would result in rapid release of heat. -Formation of one or more oxides.
Stoichiometry:
-Stoichiometry is the quantitative study of reactants and products in a chemical rxn.
Strong and Weak Electrolytes: -A ............................ electrolyte is an electrolyte that exists in solution almost entirely as ions. Most ionic solids in water completely dissociates as ions. EX: NaBr (s) → ............... + .................
-Strong -Na+ (aq)+ Br- (aq)
Reaction Yield:
-The amount of limiting reagent at the start of a rxn determines the theoretical yield. This is when all limiting reagent reacts to form the products. -This is the maximum obtainable yield. -In practice, the amount of product obtained is almost always less than theoretical yields. This is called actual yield.
Limiting Reagents:
-The reactant used up first is called limiting reagent.
Avogadro's Number and Molar Mass of an Element: -A special unit to describe a very large number of atoms. -The number of atoms in a 12-g sample of C-12 is called Avogadro's number.
-There are 6.022 x 1023 atoms in 12 g of C-12. This number is known as Avogadro's number (NA).
-Acids such as HCl, HBr, and HNO3 are called ......... acids b/c they have one acidic hydrogen per molecule. -A polyprotic acid is an acid that yields two or more acidic hydrogen per molecule.
-monoprotic
Concentration of Solutions: -When a substance is dissolved in water, it is called a solute. The water is called the ................. Very important question -What is the amount of solute in a solution? -The amount of a solute dissolved in a solution is expressed in terms of concentration. ..................... is a concentration unit to calculate the amount of the solute dissolved in a ................
-solvent -molarity, solvent
Problem 1: How many moles are there in 1.15 g of sodium?
.0500 mol
Zinc dissolves in hydrochloric acid to yield hydrogen gas: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) What mass of hydrogen gas is produced when a 7.35 g chunk of zinc dissolves in 500. mL of 1.200M HCl?
0.227 g
Five steps:
1. Write the correct chemical formulas for both reactants and products. 2. Convert the quantities into moles. 3. Use the proper conversion factors using the coefficients from the balanced equation. 4. The calculated # of moles is now converted to the required unit for the unknown quantities. 5. Make sure you have the proper unit.
Problem: Silicon tetrachloride is prepared according to the following rxn: Si (s) + Cl2 (g) Si Cl4 (l) How many moles of molecular chlorine were used to produce 0.507 mol of SiCl4?
1.01 mol
What is the average mass, in grams, of one Zn atom?
1.09 x 10-22 g
How many O atoms are in 4.39 g of CO2?
1.20 x 10^23 O atoms
Problem 4: How many oxygen atoms are there in one mole of oxygen molecule?
1.20*10^24
Problem: Chalcopyrite (CuFeS2) is a principal mineral of copper. How many kg of Cu are in 3.71x103 kg of chalcopyrite?
1.28 kg
Problem 2: How many grams of Fe would be equal to 0.025 mol Fe?
1.4 g
What is the average mass, in grams, of one Rb atom?
1.42 x 10-22g
How many F atoms are in 5.54 g of F2?
1.76 × 1023 atoms
How many Br atoms are in 2.50 g of Br?
1.88 x 10^22 Br atoms
How many moles of CF4 are there in 171 g of CF4?
1.94 mol
Calculate the average atomic mass of silver using the following data: Isotope: Ag-107, Abundance: 51.84%, Mass: 106.9051 amu Isotope: Ag-109, Abundance: 48.16%, Mass: 108.9048 amu
107.87 amu
How many total electrons are transferred in the following reaction? B2H6(g) + 3O2(g) → B2O3(s) + 3H2O(l)
12
What is the coefficient of H2O when the following equation is properly balanced? ___ Al4C3 + ___ H2O → ___ Al(OH)3 + ___ CH4
12
How many grams of Cl2 can be prepared from the reaction of 16.0 g of MnO2 and 30.0 g of HCl according to the following chemical equation? MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
13.0 g
Calculate the molar mass of (NH4)2SO4.
132.15 g/mol
What is the molecular mass of Br2?
159.8 amu
One mole of NH3 contains ...........g of the molecule.
17
RULES: 1. In free elements each atom has an oxidation number of zero. Ex: H2, O2, Be, Na, O2,, K, Al
2. For ions composed of only one type of atom, the oxidation number is equal to the charge on the ion. Ex: Fe2+ , O2-, H+, Al3+ 3. The oxidation number of oxygen in most compounds is -2. Exception: Peroxide 4. The oxidation number of hydrogen is +1, except when it is bonded to metals. In these cases (LIH, NaH, BaH2), the oxidation number is -1. 5. Fluorine has an oxidation number of -1 in all its compounds. Other halogens have negative oxidation numbers in binary compounds. They have positive oxidation number when combined w/ oxygen. 6. In a neutral molecule, the sum of the oxidation numbers of all the atoms must be zero. In a polyatomic ion, the sum of oxidation numbers of all the elements in the ion must be equal to the net charge of the ion. 7. Oxidation numbers do not have to be integers. For example, the oxidation number of O in the superoxide ion, O2 - is - 1/2.
Problem 6: What is the mass of one atom of C-12?
2.0*10^-23 g
Formaldehyde has the formula CH2O. How many molecules are there in 0.11 g of formaldehyde?
2.2 × 10^21
If 0.274 moles of a substance weighs 62.5 g, what is the molar mass of the substance, in units of g/mol?
2.28 × 102 g/mol
How many C atoms are in 5.50 g of C?
2.76 x 1023 C atoms
What is the coefficient for O2 when the following combustion reaction of a hydrocarbon is balanced? ___ C7H14 + ___ O2 → ___ CO2 + ___ H2O
21
Which one of the following does not represent 1.000 mol of the indicated substance?
26.00 g Fe
Calculate the molar mass of Ba(NO3)2.
261.3 g/mol
What is the mass of 3.50 x 1024 Ti atoms?
278 g
Aluminum metal reacts with nitric acid to produce aluminum nitrate and hydrogen gas. Identify the balanced reaction that describes this process.
2Al + 6HNO3 → 2Al(NO3)3 + 3H2
Which of the following represents a hydrogen displacement reaction?
2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2(g
Which one of the following is a redox reaction?
2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2(g)
identify the major ionic species present in an aqueous solution of K2SO4
2K+,SO4^(2-)
Molecular and Ionic Equations: -Consider dissolution of sugar in water. This is an example of molecular rxn. Reaction of ethanol in water is also another example of molecular dissolution. -For a rxn involving ions, the rxn can be represented by either a molecular equation, or a net ionic equation. Molecular Equation: Ex: Ca(OH)2 (aq) + Na2CO3 (aq) → CaCO3 (s) + .............
2NaOH (aq)
When balanced the coefficient of O2 in the following equation is __ C2H4 + __ O2 → __ CO2 + __ H2O
3
-One molecule of NH3 contains ........... hydrogens and .......nitrogen.
3,1
Zircon is a mineral with the empirical formula ZrSiO4. If all the zirconium is 90Zr, all the silicon is 28Si, and all the oxygen is 16O, what mass of oxygen is present in 10. g of zircon?
3.5 g
What is the mass of 0.0250 mol of P2O5?
3.55 g
Determine the number of moles of aluminum in 96.7 g of Al.
3.58 mol
What is the average mass of one S atom?
32.07 amu
What volume (mL) of a 0.3428 M HCl(aq) solution is required to completely neutralize 23.55 mL of a 0.2350 M Ba(OH)2(aq) solution?
32.29 mL
Molecular Weight and Formula Weight: -Molecular weight is the sum of the atomic weights of all atoms in a molecule. Ex: What is the molecular weight of H2O2?
34.02 g
What mass of C12H22O11 (sucrose) is needed to prepare 255 mL of a 0.570 M solution of sucrose in water?
49.8 g
What mass of C6H12O6 (glucose) is needed to prepare 450. mL of a 0.650 M solution of glucose in water?
52.7 g
Avogadro's number
6.02 x 10^23
Problem 3 : How many molecules are there in one mole of oxygen molecule (oxygen gas)?
6.022 * 10^23 moles of O2
Sulfur dioxide gas reacts with oxygen gas and water according to the chemical reaction below. When 4.5 g of SO2 are mixed with excess O2 and H2O, how many grams of H2SO4 are produced? 2SO2(g) + O2(g) + 2H2O(l) → 2H2SO4(l)
6.9 g
Calculate the average atomic mass of lithium using the following data: Isotope: LI, Abundance:7.5%, Mass:6.0151 amu Isotope: Li, abundance: 92.5%, Mass: 7.0160 amu
6.94 amu
Problem: Copper has two stable isotopes, Cu-62.93 amu (69.09 %) and Cu-64.9278 amu (30.91%). What is the average atomic mass of Cu?
63.55 g (amu)
Problem: Consider the following reaction: Fe2O3 (s) + 3CO (g) → 2Fe (s) + 3 CO2 (g) How many grams of iron can be produced from 1.00 x 103 g Fe2O3?
699 g
A 3.682 g sample of KClO3 is dissolved in enough water to give 375. mL of solution. What is the chlorate ion concentration in this solution?
8.01 × 10-2 M
A 50.0 mL sample of 0.436 M NH4NO3 is diluted with water to a total volume of 250.0 mL. What is the ammonium nitrate concentration in the resulting solution?
8.72 × 10-2 M
The reaction of 44.1 g of Cr2O3 with 35.0 g of Al produced 25.6 g of Cr. What is the percent yield for this reaction? 2Al + Cr2O3 → Al2O3 + 2Cr
84.9%
Which one of the following is an example of a balanced chemical reaction?
8HCl + 2KMnO4 → 3Cl2 + 2MnO2 + 4H2O + 2KCl
Solution
A homogeneous mixture of two or more substances
Solvent
A liquid substance capable of dissolving other substances
Which of the following will occur when solutions of CuSO4 (aq) are mixed?
A precipitate of BaSO4 will form; Cu2+ and Cl- are spectator ions.
Which of the following will occur when a solution of Pb(NO3)2 (aq) is mixed with a solution of KI (ag)?
A precipitate of PbI2 will form; K+ and NO3- are spectator ions.
limiting reactant
A reactant that is totally consumed during a chemical reaction, limits the extent of the reaction, and determines the amount of product.
Titration
A solution of known concentration is used to determine the concentration of another solution.
Reactants
A starting material in a chemical reaction
product
A substance produced in a chemical reaction
nonelectrolyte
A substance that dissolves in water to give a solution that does not conduct an electric current
Solute
A substance that is dissolved in a solution.
Electrolyte
A substance that is dissolved in solution and some of its molecules split or dissociate into electrically charged atoms or ions; results in electricity
Moles:
A very important unit in chemistry -A 10.0 g sample of ethanol (<3 teaspoons) contains: 131,000,000,000,000,000,000,000 molecules. It is not very easy to count all these molecules! -A mole is the quantity of a given substance that contains as many molecules or formula units as the number of atoms in exactly 12 g C-12. -Mole concept to deal w/ the number of molecules. mole = mass/ MW
Solutions of sodium hypochlorite, NaClO, are sold as bleach (such as Clorox). They are prepared by the reaction of chlorine with sodium hydroxide. If you have 1.23 mol of NaOH in solution and 1.47 mol Cl2 gas available to react, a)which is the limiting reactant? b)How many moles of NaClO could be obtained?
A) NaOH B) 45.8 g
Types of Chemical Rxns: 1. Precipitation Rxns: Two ionic substances are mixed, and a solid ionic substance forms. -A precipitate is formed during the process. -You must be able to recall the solubility rules. Ex: MgBr2 + AgNO3
Ag+(aq) + Br-(aq)--> AgBr (s)
Identify the correct net ionic equation for the reaction that occurs when solutions of AgNO3 and NH4Cl are mixed
Ag+(aq) + Cl-(aq) → AgCl(s)
Based on the solubility rules, which one of the following compounds should be insoluble in water?
AgBr
Identify the precipitate(s) formed when solutions of NH4Cl(aq), AgClO3(aq), and NaCl (aq) are mixed.
AgCl
salt
An ionic compound made from the neutralization of an acid with a base.
Redox Titrations
As mentioned earlier, redox reactions involve the transfer of electrons, and acid-base reactions involve the transfer of protons. -We sometimes need indicator for redox reactions as was the case for acid- base reactions. Certain chemicals can act as their own indicator. For example, MnO4 - is purple and Mn 2+ is pink. So when MnO4 - is converted to Mn 2+, the color change from purple to pink indicates the completion of reaction. Similarly, Cr2O7 2- is yellow, and Cr 3+ is green.
Based on the solubility rules, which one of the following compounds should be insoluble in water?
BaSO4
Identify the precipitate(s) formed when solutions of Na2SO4 (aq), Ba(NO3)2 (aq), and NH4ClO4 (aq) are mixed.
BaSO4
Balancing Chemical Equations: CH4 + O2 CO2 + H2O C4H8 + O2 CO2 + H2O H3PO3 H3PO4 + PH3 Ca + H2O Ca(OH)2 (g) + H2 Fe2(SO4)3 + NH3 + H2O Fe(OH)3 + (NH4 )2 SO4
Balancing Chemical Equations: CH4 + 2 O2 CO2 + 2 H2O C4H8 + 6 O2 4 CO2 + 4H2O 4H3PO3 3 H3PO4 + PH3 Ca + 2 H2O Ca(OH)2 (g) + H2 Fe2(SO4)3 + 6NH3 + 6 H2O 2 Fe(OH)3 + 3 (NH4 )2 SO4
Boron obtained from borax deposits in Death Valley consists of two isotopes. They are boron-10 and boron-11 with atomic masses of 10.013 amu and 11.009 amu, respectively. The atomic mass of boron is 10.81 amu (see periodic table). Which isotope of boron is more abundant, boron-10 or boron-11?
Boron-11
An organic thiol compound is 38.66% C, 9.73% H, and 51.61% S by mass. What is the empirical formula of this compound?
C2H6S
Which one of the following is an example of a balanced chemical reaction?
C3H6O + 4O2 → 3CO2 + 3H2O
A compound with an empirical formula of C2H3Br2 has a molar mass of 373.69 g/mol. What is the molecular formula?
C4H6Br4
A compound with an empirical formula of C2H4Br has a molar mass of 215.90 g/mol. What is the molecular formula?
C4H8Br2
An unknown compound with a molar mass of 155.06 g/mol consists of 46.47% C, 7.80% H, and 45.72% Cl. Find the molecular formula for the compound.
C6H12Cl2
Which of the following compounds is a nonelectrolyte?
C6H12O6- glucose
Solubility Rules: -Substances have different solubility in water. -Ethyl alcohol dissolves readily in water and is said to be soluble. -Benzene (................) has very limited solubility in water and is said to be insoluble.
C6H6
weak electrolytes are
CH3COOH, HF, HNO2, NH3, H20*
Figure 4.1 -The solution is a strong electrolytes b/c of the formation of ions in water or aqueous solution. -Let's look at the solution of methanol (used in car window washer soln.) in water. The following equation shows the shorthand notation for this process:
CH3OH (l) CH3OH (aq) Since the solution of methanol in water does NOT produce any ions, the solution is nonelectrolytes. Another word, it does not conduct electricity.
Vanadium(V) oxide reacts with calcium according to the chemical equation below. When 10.0 moles of V2O5 are mixed with 10.0 moles of Ca, which is the limiting reagent? V2O5(s) + 5Ca(l) → 2V(l) + 5CaO(s)
Ca
Based on the solubility rules, which of the following compounds should be insoluble in water?
CaCO3
Net Ionic Equation: -Strong electrolytes, like ionic compounds, are written as separate ions in solution. -Any insoluble solid substance is written in molecular form. -Write the net ionic form for the strong electrolytes in the above rxn. -Ions OH- and Na+ appear on both sides of equation. So nothing happens to these ions as the rxn occurs. They are called spectator ions. -Cancel similar ions from both sides. -What remains is the net ionic equation.
Ca^2+ (aq) + CO3 ^-2 (aq)--> CaCO3 (s)
Identify the reducing agent in the following chemical reaction. 5Fe2+(aq) + MnO4-(aq)+ 8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)
Fe^2+
The common constituent in all acid solutions is
H+
Identify the correct net ionic equation for the reaction that occurs when solutions of HNO3 and KOH are mixed?
H+(aq) + OH-(aq) → H2O(l
2. Acid-Base Rxns: As discussed earlier, acids are substances that ionic in water to produce H+ (proton), and a base is a compound that forms OH- (hydroxide) in water. Examples are HCl and Ca(OH)2.
HCL (aq) + Ca(OH)2 (aq) --> CaCl (aq) + 2 H2O (aq)
Strong electrolytes are
HCL, HNO3, HClO4, H2SO4, NaOH, Ba(OH)2, ionic compounds
common strong acids
HCl (hydrochloric acid), HBr (hydrobromic acid), HI (Hydroiodic acid), HNO₃ (Nitric acid), HClO₃ (Sulfuric acid), HClO₄ (Perchloric acid)
For which one of the following acids is chlorine in the +5 oxidation state?
HClO3
Which of the following compounds is a weak acid
HF
Which of the following compounds is a weak electrolyte?
HNO2
-What are the strong acids? -When these acids are dissolved in water, they dissociate completely forming H+ and anions. They are strong electrolytes, i.e, they conduct electricity.
Hydrochloric acid Hydrobromic acid Hydroiodic acid Nitric acid Perchloric acid Sulfuric acid
common weak acids
Hydrofluoric acid (HF), Nitrous acid (HNO2), Phosphoric acid (H3PO4), Acetic acid (CH3COOH)
Acid-Base Titrations
In titration, a solution of accurately known concentration, called a standard solution, is added to gradually to another solution of unknown concentration, until the chemical reaction between the two solutions is complete. If we know the volumes of standard solution and unknown, along with the concentration of the standard solution, we can calculate the concentration of the unknown solution. -Figure 4.21
Problem: A sample contains 6.64 g of potassium, 8.84 g chromium, and 9.52 g of oxygen. Calculate the simplest (empirical) formula.
K=.170 mol Cr=.170 mol O=.595 mol Empirical formula: K2Cr2O7
Identify the major ions present in an aqueous LiOH solution.
Li+,OH-
Which of the following represents an acid-base neutralization reaction?
LiOH(aq) + HNO3(aq) → LiNO3(aq) + H2O(l)
The mineral manganosite is a compound of 55Mn and 16O. If 77% of the mass of manganosite is due to manganese, what is the empirical formula of manganosite?
MnO
The mineral pyrolusite is a compound of 55Mn and 16O. If 63% of the mass of pyrolusite is due to manganese, what is the empirical formula of pyrolusite?
MnO2
In the following chemical reaction the oxidizing agent is 5H2O2 + 2MnO4- + 6H+ → 2Mn2+ + 8H2O + 5O2
MnO4-
-Remember that adding more solvent to a given amount of the stock solution changes (decreases) the concentration of the solution w/o changing the number of moles of solute present in the solution. Mol of solute before dilution = mol of solute after dilution Remember: Molarity = mole / V (in liters) If you solve for mole:
Moles = molarity x V
Using the redox reaction below determine which element is oxidized and which is reduced. 4NH3 + 3Ca(ClO)2 → 2N2 + 6H2O + 3CaCl2
N is oxidized and Cl is reduced
N2 (g) + 3 H2(g) → 2 NH3 (g) Mol ____ _____ _____ Mass, g ____ _____ _____
N2 (g) + 3 H2(g) → 2 NH3 (g) Mol 1 3 2 Mass, g 28 6 34
Which of the following compounds is a weak base?
NH3
Ammonia reacts with hydrochloric acid to produce ammonium chloride. Identify the balanced reaction that describes this process.
NH3 + HCl → NH4Cl
A weak base in water dissociates only partially. The water molecule is involved in the reaction. Ammonia is a weak base and in water it forms ......... and ............... ions.
NH4+, OH-
Identify the major ionic species present in an aqueous solution of NH4ClO4.
NH4+,ClO4-
Which of the following is NOT a redox reaction?
NH4Cl(aq) + AgNO3 → NH4NO3(aq) + AgCl(s)
ammonium hydroxide nitrate carbonate sulfate
NH4^+1 OH^-1 NO3^-1 CO3^-2 SO4^-2
Identify the major ionic species present in an aqueous solution of Na2CO3.
Na+,CO3^(2-)
Problem: An analysis of sodium dichromate gives the following %mass: What is its formula? 17.5 % Na, 39.7% Cr, and 42.8% O.
Na- 0.701 mol Cr- 0.763 mol O- 2.675 mol formula: Na2Cr2O7
Problem: What are the mass percent of Na, C, and O in sodium carbonate?
Na- 43.4% C- 11.3% O-45.3%
When 22.0 g NaCl and 21.0 g H2SO4 are mixed and react according to the equation below, which is the limiting reagent? 2NaCl + H2SO4 → Na2SO4 + 2HCl
NaCl
Ammonia reacts with oxygen to form nitric oxide and water vapor: 4NH3 + 5O2 → 4NO + 6H2O When 40.0 g NH3 and 50.0 g O2 are allowed to react, which is the limiting reagent?
O2
phosphate hydrogen phosphate perchlorate chlorate permanganate
PO4 ^-3 HPO4^-2 ClO4^-1 ClO3^-1 MnO4^-1
Ex: The reaction of ammonia gas with water to yield ammonium and hydroxide ions. -Table 4.1
Pb (NO3)2 +KF--> PbI2 (s) + KNO3 (aq)
Identify the correct net ionic equation for the reaction that occurs when solutions of Pb(NO3)2 and NH4Cl are mixed.
Pb2+(aq) + 2Cl-(aq) → PbCl2(s)
common cation names
Potassium K+ rubidium Rb+ silver Ag+ sodium Na+ strontium Sr+ tin II Sn^2+ zinc Zn^ 2+ nickel Ni^2+
Na (s)+ H2O NaOH (aq) + H2 (g) What are the reactants or starting materials? ................................ What are the products? .................................
R- Na, H2O P-NaOH, H2
Determining Formulas: Empirical (Simplest) Formula from the Composition: Compound Simplest Formula Molecular Formula Sodium chloride Water Hydrogen peroxide Ethene
Sodium chloride: NaCl, NaCl Water: H2O, H2O Hydrogen peroxide: HO, H2O2 Ethene: CH2, C2H4 Glucose: CH2O, C6H12,O6
molecular mass
The sum of the masses of all the atoms in a molecule; sometimes called molecular weight.
-The compounds that can completely ionize in water are called strong electrolytes.
They are good conductors of electricity. Ex: CaCl2 (s) Ca2+ (aq) + 2 Cl- (aq)
Problem: 1.20 g Zn react with 0.59 g sulfur to form zinc sulfide compound. What is the empirical formula of the product?
Zn-0.1835 S- 0.0184 empirical formula: ZnS
combustion reaction
a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light
neutralization reaction
a reaction in which an acid and a base react in an aqueous solution to produce a salt and water
metathesis reaction (double displacement reaction)
a reaction that involves the exchange of parts between two compounds
aqueous solution
a solution in which water is the solvent
Ex: Titanium is prepared according to the following rxn: TiCl4 (g) + 2 Mg (l) Ti(s) + 2MgCl2 (l) If 3.54 x10 7 g of TiCl4 are reacted w/ 1.13x107 g of Mg, a. calculate the theoretical yield of Ti in grams. b. calculate the %yield if 7.91 x 106 g of Ti are obtained.
a) 1.13 *10^7 b) 88.6 g
Problem: The elemental analysis of acetic acid shows 39.9% C, 6.7% H, and 53.4% O. a) Determine the empirical formula. b) Determine the molecular formula if molecular weight is 60 amu.
a) CH2O b) C2H4O2
Problem: Urea (NH2)2CO is prepared by reacting ammonia with CO2: NH3 (g) + CO2 (g) (NH2)2 CO (aq) + H2O 613.4 g ammonia are allowed to react w/ 1452 g CO2. a. Which one is the limiting reagent? b. Calculate the mass of urea formed. c. How much of the excess reagent (in g) is left at the end of the rxn?
a) NH3 B)mass urea= 1080 C)662 g
Problem: Write down balanced rxns for the following ionic species dissolved in water: a) sodium bromide b) barium fluoride c) potassium iodide
a) NaBr (s)--> Na+ (aq) + Br - (aq) b) BaF2 (s)--> Ba^2+(aq) + 2F- (aq) c) KI (s) --> K+ (aq) + I-
Problem: Write balanced net ionic equations for the following: a. calcium chloride and sodium carbonate b. lead (II) nitrate and potassium hydroxide solutions c. barium bromide and ammonium carbonate d. silver nitrate and potassium sulfide
a) ca^2+ (aq) + CO3^-2 (aq) --> CaCO3 (s) b) Pb^2+(aq) + 2OH(aq) --> Pb(OH)2 (s) c) Ba^2+ (aq) + CO3 ^2- (aq) --> BaCO3 (s) d) 2Ag^+ (aq) + S^2- (aq) --> Ag2S (s)
standard solution
added gradually to another solution of unknown concentration, until the chemical reaction between the two solutions is complete
common cation names
aluminum- Al^3+ ammonium- NH4^+ barium- Ba^2+ cadmium- Cd^2+ calcium- Ca^2+ Cesium- Cs+ Chromium III Cr^3+ Cobalt II Co^2+
gravimetric analysis
an analytical technique based on the measurement of mass
Disproportionation reaction
an element in one oxidation state is simultaneously oxidized and reduced
displacement reaction
an ion (or atom) in a compound is replaced by an ion (or atom) of another element
-What are the weak acids?
any acids other than the 7 acids
Excess reagents
are the reactants present in quantities more than necessary to react with the quantities of the limiting reagent.
Problem: Which of the following statements is correct for the following reaction? 4NH3 (g) + 5 O2 (g) 4NO (g) + 6H2O (g) a. 6 g H2O are produced for every 4 g of NH3 reacted. b. 1 mol of NO is produced per mole of NH3 reacted. c. 2 mol of NO are produced for every 3 mol O2 reacted
b
common anions
bromide Br- carbonate CO3^-2 chlorate ClO3^- chloride Cl- cyanide CN- dichromate Cr2O7^-2 dihydrogen phospate H2PO4^- Fluoride F-
Balancing Simple Oxidation-Reduction Equations: -A reaction must be both mass as well as charge balanced. -Consider the following rxn: Zn (s) + Ag+ (aq) → Zn2+ (aq) + Ag (s) This rxn is not ...................... balanced.
charged
Chemical Reactions and Chemical Equations: -representation of a chemical rxn in terms of
chemical formulas
-When an ionic ................ dissolves into water, the ................... are released from their crystal structure and are free to move throughout the solution. -To show that the substance is soluble in water its formula must be followed by "(aq)".
compound, ions
The distinguishing characteristic of all electrolyte solutions is that they
conduct electricity
common cation names
copper II Cu ^2+ Hydrogen H+ iron II Fe^2+ iron III Fe^3+ lead II Pb^2+ Lithium Li^+ Magnesium Mg^2+ Manganese Mn ^2+ Mercury I Hg2 ^2+ Mercury II Hg^2+
HCl is called a monoprotic acid. H2SO4 is called a ............... acid. H3PO4 is called a ............ acid.
diprotic, triprotic
monoprotic acid
each unit of the acid yields one hydrogen ion upon ionization
diprotic acid
each unit of the acid yields two hydrogen ions upon ionization
oxidizing agent
electron acceptor
reducing agent
electron donor
redox reaction
electrons are transferred
half-reaction
explicitly shows the electrons involved in a redox reaction
hydronium ion
hydrated proton, H3O+
common anions
hydride H- hydrogen phosphate HPO4^2- hydrogen carbonate or bicarbonate HCO3^- sulfate or bisulfate HSO4- hydroxide OH- iodide I- nitrate H^2- nitride N^3- nitrite NO2^- oxide O^2-
stoichiometric amounts
in the proportions indicated by the balanced equation
-When solutes made up of ions are dissolved in water, ................ are released into the water.
ions
spectator ions
ions that are not involved in the overall reaction
combination reaction
is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product).
precipitate
is an insoluble solid that separates from the solution
mole
is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12
decomposition reaction
is the breakdown of a compound into two or more components
The formula weight (FW) of a substance
is the sum of the atomic weights of all atoms in a formula unit of the compound whether molecular or not.
Molarity (M) = (mol solute / liters of solution) -The symbol [ ]
is used represent the concentration of the species.
-When solutes made of molecules are dissolved in water, ................. are released into the water.
molecules
-Molecular weight is a multiple of the empirical weight. Molecular weight = n x empirical formula n is the number
of empirical formula unit in the molecule
atomic mass unit
one twelfth the mass of a carbon-12 atom
common anions
permangate MnO4^- peroxide O2^2- phosphate PO4^3- sulfate SO4^3- sulfide S^2- sulfite SO3^2- thioyanate SCN- Perchlorate CLO4^-
Bronsted base
proton acceptor
Bronsted acid
proton donor
Weak acids: These are the acids that dissociate partially in water; i.e., only a small fraction of all of the acid molecules present in solution actually
reacts with the solvent.
Oxidation Number: -The oxidation number allows us to keep track of the electron exchange in a
redox rxn. -To keep track of e's in redox rxns. -The number of charges the atom would have in a molecular or ionic compound if electrons were transferred completely.
precipitation reaction
results in the formation of an insoluble product, or precipitate
Neutralization Reactions: -An acid reacts w/ a base to form water and a ..............
salt
ionic equation
shows dissolved species as free ions
net ionic equation
shows only the species that actually take part in the reaction
A solution can be
solid, liquid, or gas
-A substance that is dissolved in water or some other medium is called a ................., and water is called .................
solute, solvent
Hydration
solution process with water as the solvent
Indicators
substances that have distinctly different colors in acidic and basic media
The Law of Definite Proportions tells us
that the elements in a chemical compound always combine in a definite ratio by mass.
A characteristic of strong electrolytes is
that the solute is assumed to be 100 percent dissociated into ions in solution. (By dissociation we mean the breaking up of the compound into cations and anions)
theoretical yield
the amount of product that would result if all the limiting reagent reacted
concentration of a solution
the amount of solute present in a given quantity of solvent or solution
quantitative analysis
the determination of the amount or concentration of a substance in a sample
molecular equation
the formulas of the compounds are written as though all species existed as molecules or whole units
reduction reaction
the half-reaction that involves the gain of electrons
oxidation reaction
the half-reaction that involves the loss of electrons
Solubility
the maximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature
actual yield
the measured amount of a product obtained from a reaction
oxidation number
the number of charges an atom would have in a molecule if electrons were transferred completely in the direction of the atoms with the higher electronegativity
Molarity
the number of moles of solute per liter of solution
percent composition by mass
the percent by mass of each element in a compound
equivalence point
the point at which the acid has completely reacted with or been neutralized by the base
Dilution
the procedure for preparing a less concentrated solution from a more concentrated solution
chemical reaction
the process by which one or more substances change to produce one or more different substances
percent yield
the proportion of the actual yield to the theoretical yield
Stoichiometry
the quantitative study of reactants and products in a chemical reaction
reversible reaction
the reaction can occur in both directions
mole method
the stoichiometric coefficients in a chemical equation can be interpreted as the number of moles of each substance
-Mole Method:
the stoichiometric coefficients in a chemical equation can be interpreted as the number of moles of each substance.
excess reactant
the substance that is not used up completely in a reaction
atomic mass
the weighted average of the masses of the isotopes of an element
chemical equation
uses chemical symbols to show what happens during a chemical reaction
-Molarity is defined as the number of moles of solute per liter of solution. -Molarity represents a ratio in which the quantity of solute, in moles, is divided by the total ............... of the mixture, in liters
volume
-A ....................... electrolyte forms a relatively small percent of ions. - ....................... electrolytes are generally molecular substances
weak, weak
triprotic acid
yield three H+ ions