Chem Chapter 3
which of the following reactions would have an enthalpy change equal to deltaHfº? - C(graphite) + O2(g) --> CO2 (g) - 3O2(g) --> 2O3 (l) - Hg (s) + S (s) --> HgS (s) - CH4 (g) --> C(graphite) + 2H2 (g) - Fe (s) + 3/2Cl2 (g) --> FeCl3 (s)
- C(graphite) + O2 (g) --> CO2 (g) - Fe (s) + 3/2Cl2 (g) --> FeCl3
if 1.0 mole of neon, 2.0 moles of helium, and 3.0 moles of argon are mixed, what is the mole fraction of helium?
0.33
a mixture of gases contains 1.50 mol of O2, 0.75 mol of He, and 2.25 mol of N2. the total pressure exerted by the mixture is equal to 2.50 atm. what is the partial pressure of the He?
0.418 atm
list the steps in order for calculating the molar mass of nitrogen gas
1. identify that nitrogen exists as N2 and find the atomic mass of nitrogen on the periodic table 2. multiply the atomic mass of nitrogen by 2 in order to calculate its molecular mass 3. report the molar mass of nitrogen as 28.02 g/mol
classify each equation according to type 1. Pb(NO3)2 (aq) + 2NaCl (aq) --> PbCl2 (s) + 2NaNO3 (aq) 2. Pb(2+) (aq) + 2Cl- (aq) --> PbCl2(s) 3. Pb(2+) (aq) + 2NO3- (aq) + 2Na+ (aq) --> PbCl2 (s) + 2Na+ (aq) + 2NO3- (aq)
1. molecular equation 2. net ionic equation 3. total ionic equation
what is the mass of Cs present in 15.0 g of cesium acetate, formula CsCH3COO?
10.4 g 132.9 g Cs/191.9 g CsCH3COO = 69.25% 69.25/100 x 15.0= 10.4 g
Calculate ΔH°rxn for the reaction A + 2B → 2C using the ΔH°f values given below.
2(c) -(a) -2(b)
what is the correct mathematical operation to calculate the number of molecules in 2 mol of CH4?
2.0 mol x 6.022 x 10^23 molecules/mol
the density of a gas is 2.49 g/L at 3.00 atm and 25ºC. calculate the molar mass of the gas
20.3 g/mol
The molecular formula of a compound having an empirical formula NH2 (ℳ = 32.05 g/mol) is N_________H________
2;4
Consider the following: 2A -> B; deltaH = x2B -> C; deltaH = y What is the total enthalpy change for the reaction 4A -> C?
2x + y (to obtain the desired equation, equation 1 must be multiplied by 2 and added to equation 2)
When hydrogen gas is passed over powdered iron(III) oxide, iron metal and water vapor are formed. Which of the following is the correct balanced equation for this process?
3H2(g) + Fe2O3(s) → 2Fe(s) + 3H2O(g)
what is the mass percent of oxygen in aluminum oxide (Al2O3)?
47.08%
what correctly reflects the ratio of Avogadro's number?
6.022 x 10^23 entities/1 mol
a small piece of Cr metal reacts with dilute HNO3 to form H2 (g), which is collected over water at 18 C in a large flask. the total pressure in the flask is 753 mmHg. determine the partial pressure of the H2 present
738 mmHg
how many grams of KMnO4 correspond to 3.13 x 10^22 formula units of KMnO4?
8.21 g of KMnO4
Balance the unbalanced equation given and match each substance to the correct coefficient as indicated. Al2S3(s) + H2O(l) → Al(OH)3(aq) + H2S(g)
Al2S3 1 H2O 6 Al(OH)3 2 H2S 3
a salt is dissolved in a bath of water. calculate the total amount of heat taken in or give out by the system (in J) if the temperature of m(water) grams of water decreases from initial temp C to final temp C when m(salt) grams of salt is added to it. assume the specific heat capacity of the solution is C(s)J/gK
C(s) x (m(water) + m(salt)) x (T(final) - T(initial))
Two solids of identical mass, A and B, are analyzed using identical calorimeters (containing the same amount of water, each at room temperature). When the solids are heated to the same initial temperature and placed in their calorimeters, the final temperature of solid A's calorimeter is higher than that of B. What can we infer from this?
Csolid A > Csolid B
place the halogens in order from most reactive to least reactive: Br2 Cl2 I2 F2
F2 Cl2 Br2 I2
what is the empirical formula of a compound that consists of 0.039 moles of iron atoms combined with 0.052 moles of oxygen atoms?
Fe3O4 0.052/0.039= 1.33, which gives a ratio of 1:1.33 mult by 3 to get integers 3:4, thus Fe3O4
For a reaction that proceeds through a series of steps, ΔH(overall)=ΔH(1)+ΔH(2)+ΔH(3) (and so on and so forth.) This is a restatement of ______ law
Hess's
the molecular formula of a compound having an empirical formula NH2 (ℳ= 32.05 g/mol) is N__H__
N2H4
a nitrogen oxide contains 30.45% N mass. if the molar mass of the compound is 90. +- 5 g/mol, what is its molecular formula?
N2O4
match each species to its correct oxidation number: O in O2 Na in NaCl O in H2O Fe in FeCl3
O in O2: 0 Na in NaCl: +1 O in H2O: -2 Fe in FeCl3: +3
match each element with its most common oxidation number: O H F Mg
O: -2 H: +1 when bonded to other nonmetals F: -1 Mg: +2; Mg will form the monatmic ion Mg2+, with a charge and oxidation number of +2
Match the effects of the following combinations of Reactions 1 and 2 with the reaction resulting from these combinations.Reaction 1: A → 2CReaction 2: C → B
Rxn 1 + (-Rxn 2)--- A + B --> 3C Rxn 1 + 2(Rxn 2)--- A --> 2B (-Rxn 1) + (-Rxn 2)--- B + C --> A
what statements correctly describe a total ionic equation?
The total ionic equation includes all ions, including spectator ions.Charges must be included where appropriate in this type of equation.Charges and atoms must be balanced in this type of equation.
Menthol is a compound of carbon, hydrogen, and oxygen. When .1595 g of menthol underwent a combustion alalysis, .449 g of CO2 and .184 g of H2O were produced.
There are 2.04 × 10-2 moles of H in the sample.The mass of C present is 0.123
what correctly defines a precipitate?
a solid product that separates from a solution
Which of the following species should be included in the net ionic equation for the precipitation reaction given?- ZnSO₄ + CaCl₂ → CaSO₄ + ZnCl₂ a. Ca²⁺ b. SO₄²⁻ c. ZnCl₂ d. CaSO₄ e. Zn²⁺
a. Ca²⁺ b. SO₄²⁻ d. CaSO₄ (this is an insoluble sulfate and will precipitate from solution)
The equation 3Ni2+ (aq) + 2Cr (s) → 2Cr3+ (aq) + 3Ni (s) represents a redox reaction.In this reaction Ni2+ is the species _____ and is the _____ agent. a) reduced; oxidizing b) oxidized; oxidizing c) reduced; reducing d) oxidized; reducing
a. reduced; oxidizing Ni2+ gains electrons to become N
a barometer, which is a device used to measure ____ pressure, consists of a vacuum tube containing a column of liquid such as mercury. the atmospheric pressure is proportional to the _____ of the liquid column
atmospheric; height
true or false: in an open-end manometer, the difference in heights is the pressure in the flask
false: that is a close-end manometer. in an open-end manometer, the difference in heights is the pressure difference between the flask and atmospheric pressure
how is pressure defined mathematically?
force/area
the pressure in a gas arises because the particles of a gas strike each other and the walls of their container exerting a ____. the greater the number of gas particles in a particular volume, the ____ the pressure within the gas
force; greater
match each symbol used in balanced chemical equations with the correct designation g l s aq
g- gas l- liquid s- solid aq- aqueous
the mole relates the atomic mass of an element expressed in amu with the mass of 1 mole of that element expressed in ____. the mass of 1 mole of oxygen atoms is therefore equal to ____g (to 4 sig figs)
grams; 16.00
Use the equation for specific heat capacity to determine the function needed to solve for the variables associated with temperature change.
heat→cmassΔT Mass of substance→q/c*ΔT Change in temperature→q/mass*c Specific heat capacity→q/mass*ΔT
the species oxidized shows an
increase in oxidation number
as the temperature of a gas sample at constant pressure increases, the volume of the gas will ___ and there will be ____ gas particles in the same space. the density of a gas at constant pressure therefore ___ as temperature increases
increase; fewer; decreases
atmospheric pressure arises due to the force exerted by the air above the Earth. at higher altitudes, the mass of the air above the earth is ____ than at sea level, and atmospheric pressure therefore ____ with altitude
less; decreases
oxidation is defined as the ____ of electrons while reduction is the ____ of electrons
loss; gain
gases tend to have ____ densities than either liquids or solids, and their ____ change greatly with changes in temperature or pressure
lower; volumes
which of the following gives the correct procedure to calculate the mass of a substance given the number of moles?
moles x molar mass
oxidation, or the loss of electrons, will result in an element becoming ____ positive. this element will show a(n) _____ in oxidation number. reduction, the gain of electrons, will cause an element to become ____ positive and the element will show a(n) _____ in oxidation number
more; increase; less; decrease
when converting a pressure from units of torr to millimeters of mercury (mmHg) the numeric value will ____
not change
what is the correct mathematical operation to convert the number of atoms of a sample to the number of moles?
number of atoms/Avogadro's number no. of atoms x 1 mol/6.022 x 10^23 atoms= mols
the species that shows a decrease in oxidation number is the
oxidizing agent (decrease in oxidation number indicates reduction)
the SI unit for pressure is the
pascal (Pa)
generate the equation A + 2B --> 2D from a combination of the reactions providedreaction 1 : A + 2B --> 2Creaction 2 : C --> Dhow must reactions 1 and 2 be combined to sum to the overall reaction?
reaction 1 + 2(reaction 2) by doubling reaction 2, C will cancel
a precipitation reaction is a reaction in which two or more water-____ ionic compounds react in aqueous solution to form one or more _____ precipitates
soluble; insoluble
Thermodynamic parameters are usually calculated for compounds under_________conditions, since values tend to vary somewhat with conditions. To be in this state, a gas must have a pressure of 1_______________and a solution must have a concentration of 1___________________
standard; bar; molar
The compounds depicted are _________ isomers because they have the same ____________formula but have different _____________formulas.
structural; molecular; structural
what is the only additional information needed to calculate the empirical formula of a compound if the masses of each element of the compound are provided?
the molar mass of each compound
a reaction may be carried out so that a gaseous product is collected over water. which statement describes how to calculate the pressure due to the product gas alone?
the vapor pressure of the water must be subtracted from the barometric pressure
at STP, the density of argon is ___
twice the density of neon
in stoichiometry problems involving reactions in solution, the molarity of a solution is used to convert between the ____ of a solution and the number of ____ of solute
volume; moles
specific heat capacities are tabulated in units of J/gk, but most temperature measurements are made in units of celsius. if a system is initially at 5 C and is heated to 10 C, what is the change in temperature in kelvins?
+5 (since Kelvin and Celsius units have the same magnitude, it is also correct to report specific heat capacities in units of J/g x C)
If 8.50 g of phosphorus reacts with hydrogen gas at 2.00 atm in a 10.0-L container at 298 K, calculate the moles of PH3 produced as well as the total number of moles of gas present at the conclusion of the reaction. P4(s) + 6H2(g) --> 4PH3(g)
- 0.274 mol of PH3 are produced - the total amount of gas present is 0.679
32 g of ZnS reacts according to the balanced equation 2ZnS (s) + 3O2 (g) → 2ZnO (s) + 2SO2 (g); ΔH = -879 kJ. Select all the options that correctly reflect parameters that can be derived from the information given.
- 15.8 g of O2 are required to react completely with the ZnS present - this reaction releases 144 kJ of energy - 0.328 mol of ZnS reacts
Two equations must be manipulated in order to generate the overall equation Br2 + 2NO --> 2NOBr. Select the two chemical equations from below that can be arranged and added together to generate the overall equation (Note: the equation(s) may need to be reversed or multiplies by a constant.)
- 2NOBr --> NOBr2 + NO (if the equation 2NOBr --> NOBr2 + NO is reversed, it can be added to the equation Br2 + NO --> NOBr2 to give the desired equation - Br2 + NO --> NOBr2
which combination of solutions will produce one or more precipitates? - MgCl2(aq) + Na2SO4 (aq) - Ba(NO3)2 (aq) + KI(aq) - AgNO3 (aq) + NH3Br(aq) - CaBr2 (aq) + K3PO4 (aq)
- AgNO3 (aq) + NH3Br(aq) (AgBr is insoluble in water) - CaBr2 (aq) + K3PO4 (aq) (Ca3(PO4)2 is insoluble in water)
a compound has the empirical formula CH2O. what are the possible options for the molecular formula of this compound? - C2H4O2 - C3H2O - C6H12O6 - CH2O - C3H5O2
- C2H4O2 - C6H12O6 - CH2O
Which of the following statements correctly describe the two reactions outlined below? Reaction 1: A -> B deltaH = +50 kJ Reaction 2: C -> D deltaH = -100 kJ
- Reaction 2 is exothermic - The surroundings near Reaction 1 will become colder as it proceeds - Reaction 2 releases twice as much energy as Reaction 1 absorbs
which of the following statements correctly describe the mole fraction of a component in a mixture? - a mole fraction can be converted to a mole percent by multiplying by 100 - in a mixture of gases, the partial pressure of each gas is proportional to it's mole fraction - the mole fraction of a component can range from 0 to 100 - a mole fraction is a unitless quantity - a mole fraction can be calculated only when there are two components in the mixture
- a mole fraction can be converted to a mole percent by multiplying by 100 - in a mixture of gases, the partial pressure of each gas is proportional to it's mole fraction - a mole fraction is a unitless quantity - a mole fraction can be calculated only when there are two components in the mixture
what statements correctly describe a molecular equation?
- a molecular equation will not include any charges on any of the species - this equation represents all reactants and products as if they were intact and undissociated
describe the steps required to decide whether or not precipitate forms when two aqueous solutions are mixed
- any product that is insoluble in water will be a precipitate - the first step is to identify the ions present in each solution - the products of the reaction are identified from the possible cation-anion combinations
which of the following statements describe combustion analysis correctly? - combustion analysis involves burning a compound in O2 - all the oxygen in the CO2 produced comes from the original compound being analyzed - the mass of hydrogen in the compound is determined from the amount of H2O produced - combustion analysis can only be used to analyze compounds containing C, H, and O - every 1 mole of carbon in the compound will produce 1 mole of CO2
- combustion analysis involves burning a compound in O2 - the mass of hydrogen in the compound is determined from the amount of H2O produced - every 1 mole of carbon in the compound will produce 1 mole of CO2
correctly describe the properties of gases
- gases have relatively low densities - temperature changes have a large effect on the volume of a gas - gases are much more compressible than liquids or solids
which of the following ions always form soluble ionic compounds? -SO4-(2) -NH+(4) -NO-(3) -PO3-(4) -group 1A cations
- group 1A cations - NH+(4) - NO-(3)
Which of the following actions are permitted in balancing a chemical equation? Select all that apply. - adding reactants or products - inserting coefficients in front of formulas of reactants and products - multiplying all coefficients by a common factor - altering the formulas of reactants or products
- inserting coefficients in front of formulas of reactants and products - multiplying all coefficients by a common factor
Which of the following correctly describe isomers? - isomers are compounds with the same molecular formula - isomers are compounds with the same chemical properties - isomers are compounds with the same molar mass - isomers are compounds with the same empirical formula
- isomers are compounds with the same molecular formula - isomers are compounds with the same molar mass - isomers are compounds with the same empirical formula
Which of the following steps are necessary to calculate the mass percent of oxygen in acetic acid (CH3COOH) - multiply the moles of oxygen in the molecular formula by the molar mass of oxygen and then divide by the mass of one mole of acetic acid - multiply the answer by 100 to find the mass percent of oxygen in acetic acid - calculate the molar mass of acetic acid from its formula - determine the number of molecules of acetic acid in the sample
- multiply the moles of oxygen in the molecular formula by the molar mass of oxygen and then divide by the mass of one mole of acetic acid - multiply the answer by 100 to find the mass percent of oxygen in acetic acid - calculate the molar mass of acetic acid from its formula
CO (g) can be produced by the reaction of coal with steam, as shown by the balanced equation: H2O (g) + C (s) → CO (g) + H2 (g). Which of the following options correctly reflect the steps required to calculate ΔH for this reaction, given the information shown below? Select all that apply.Reaction 1: H2 (g) + 12O2 (g) → H2O (g); ΔH = -242.0 kJReaction 2: 2CO (g) → 2C (s) + O2 (g); ΔH = +221.0 kJ
- reaction 2 must be reversed and divided by 2 - deltaH = +131.5 kJ
which of the following pieces of information is/are necessary to calculate the molar mass of a compound? - the atomic masses of each of the elements that make up the compound - the formula of the compound - the mass of a sample of the compound - the physical properties of the compound
- the atomic masses of each of the elements that make up the compound - the formula of the compound
Given the balanced equation CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + H2O (l) + CO2 (g), select all the statements that correctly describe how to calculate the mass of CaCO3 that will react with 72.5 mL of a 0.250 M solution of HCl. (The molar mass of CaCO3 is 100.09 g/mol.)
- the conversion factor 0.250 mol HCl/1 L HCl will be used as written in the calculation - 0.907 g of CaCO3 will react
Which of the following values are needed to solve for the heat capacity of a heated unknown solid when it is placed in a coffee cup calorimeter? Select all that apply.
- the mass of the solid - the initial temperature of the solid - the final temperature of the system - the mass of the water in the cup - the initial temperature of the water
what describes the steps required to determine the empirical formula of a compound from the mass percent?
- the mass percentage of each element is converted to moles using the mass formula: mass/molar mass - the ratio of atoms of each element must be a ratio of integer numbers - if a compound contains 52% mass of C, it can be assumed that there are 52 g of C in 100 g of the compound
one molecule of Br2 has a mass of ____ amu; thus, one mole of Br2 molecules has a mass of ___ grams
159.8; 159.8
1.52 x 10^24 atoms of Au correspond to ____ mol of Au atoms. answer to 3 sig figs using decimal notation (NOT sientific notation)
2.52 (1.52 x 10^24 atoms Au x 1 mol Au/6.022 x 10^23 atoms Au
84 g of a metal at an initial temperature of 72°C releases 553 J of heat. Calculate the final temperature of the metal if its specific heat capacity is 0.13 J/g⋅K.
21ºC
one formula unit of KOH has a mass of ____ amu; hence, 1 mol of KOH has a mass of ____g (4 sig figs)
56.11; 56.11
Which of the following are equivalent to 652 mmHg A) 1.17 atm B) 5.66x10^3 kPa C)0.858 atm D) 86.9 kPa
C and D
in order to calculate the mass of an element in a given sample of a compound, the mass of the compound is multiplied by the mass ____ of the element in the compound
fraction
the particles in a gas have a ___ distance between them than the particles of a liquid or a solid and their movement is random. gas particles therefore move ___ freely than the particles of solids or liquids
greater; more
a close-end _______ is used for measuring gas pressure in an experiment. in the close-ended design, if a gas is present in the flask, the gas will exert a pressure on the mercury column closest to it, causing the column on the left to be ____ than the column on the right
manometer; lower
the species that shows an increase in oxidation number is the
reducing agent (an increase in oxidation number indicates oxidation)
true or false; an oxidation number is not the same as an actual charge on an ion
true. an oxidation number is the charge an atom WOULD have if electrons were always transferred, but is not the actual charge. although the oxidation number for a monatomic ion is equal to its charge, not all species involved in redox reactions are charged or become charged
which of the following statements correctly describe molar mass? - the term "molar mass" applies to compounds but not to elements - the periodic table can be used to calculate the molar mass of any substance - when referring to the mass per mole of an entity, the term "entities" could refer to atoms, ions, molecules, or formula units - the molar mass is commonly given in units of kg/mol - the molar mass of a substance is the mass per mole of its entities
- the periodic table can be used to calculate the molar mass of any substance - when referring to the mass per mole of an entity, the term "entities" could refer to atoms, ions, molecules, or formula units - the molar mass of a substance is the mass per mole of its entities`
what correctly describes a precipitation reaction?
- this type of reaction usually involves ionic compounds - this type of reaction forms one or more insoluble products - this type of reaction often occurs in aqueous solution
If an exothermic reaction heats a system with a total mass of 10 grams from 20oC to 30oC what is the total enthalpy change? Assume that the specific heat of the system is 2 J/g⋅K.
-200 J (reaction is exothermic; if the reaction heats the calorimeter, the reaction must be GIVING OUT heat and deltaHrxn must have a negative sign deltaH= -qp = -(10 g )(2 J/g x K)(30ºC - 20ºC) = -200 J
Which of the following statements correctly describe the empirical formula for a compound? -Different compounds can have the same empirical formula. -The empirical formula of a compound gives the smallest whole number ratio of atoms in a compound - the empirical formula of a compound gives the molecular structure of a compound - compounds with the same empirical formula have similar chemical properties
-Different compounds can have the same empirical formula. -The empirical formula of a compound gives the smallest whole number ratio of atoms in a compound.
Which of the following statements correctly describe the molecular formula for a compound? -It is possible that the molecular formula for a compound is the same as its empirical formula. - there are no examples of compounds that are different but have the same molecular formula -A molecular formula may give little or no information about the structure of the compound. -The molecular formula gives the actual number of each type of atom in a compound.
-It is possible that the molecular formula for a compound is the same as its empirical formula. -A molecular formula may give little or no information about the structure of the compound. -The molecular formula gives the actual number of each type of atom in a compound.
which of the following statements describe the information that can be gained from a balanced chemical equation? - how fast a given reaction proceeds -The physical states of reactants and products, often. -The relative quantities (moles) of substances involved. -The identities of substances involved. - the temperature at which a reaction is carried out
-The physical states of reactants and products, often. -The relative quantities (moles) of substances involved. -The identities of substances involved.
which of the following correctly reflect Avogadro's number? - the mole contains 6.022 x 10^23 entities - for a pure substance, the mole specifies only the number of entities in a sample - the number of entities in a mole is called Avogadro's number - the mole is abbreviated mo.
- the mole contains 6.022 x 10^23 entities - the mole contains 6.022 x 10^23 entities
what items of information are necessary to calculate the mass percent of an element in a compound? - the mass of the compound - the number of moles of the element in one mole of the compound - the formula of the compound - the number of molecules/formula units of the compound - the molar mass of the compound
- the number of moles of the element in one mole of the compound - the formula of the compound - the molar mass of the compound
which statements correctly describe specific heat capacity (c)?
-The units of specific heat are J/g*K (specific heat capacity is, by definition, quantity of heat required to change the temp of 1 gram of an object by 1 K) .-The symbol for specific heat is c. -The specific heat for a substance has the same value regardless of the size of the sample. (the amount of heat required to raise the temp of 1 g of substance by 1 K remains the same, regardless of the size of the sample)
arrange the necessary steps in order for finding the molecular formula of an unknown compound from mass percent data
1. Assume that the sample contains 100.0 g of compound and express each mass percent as a mass in grams 2. Convert the mass of each element to moles of each element 3. Derive the empirical formula looking for the simplest whole number ratio of moles 4. Divide the molar mass of the compound by the mass of the empirical formula in order to find a multiple that is an integer 5. multiply each subscript of the empirical formula by the integer multiple
correctly order the steps necessary to determine the molecular formula for a compound using combustion analysis data
1. Determine the masses of carbon and hydrogen from the masses of CO2 and H2O respectively. 2. Determine the mass of oxygen, if present, by subtracting the masses of carbon and hydrogen from the total mass 3. Determine the number of moles of each element in the compound and hence the empirical formula 4. determine the molecular formula using the empirical formula and the molar mass
Arrange following gases in order of increasing density
1. helium at 1 atm and 273 K 2. neon at 1 atm and 273 K 3. neon at 2 atm and 273 K 4. neon at 2 atm and 73 K
Correctly order the steps necessary to solve for the mass of a product, or second reactant required, given the mass of one of the reactants in a chemical process
1. write a balanced equation for the reaction 2. convert the given mass into moles using molar mass. convert moles of A to moles of B using a conversion factor derived from the balanced equation 3. convert the moles of the second substance to mass using its molar mass
what is the net equation when the following reactions are summed? 2C(graphite) + 3H2 (g) --> C2H6 (g) C2H4 (g) --> 2C)graphite) + 2H2 (g)
C2H4 (g) + H2 (g) --> C2H6 (g)
match each compound to the correct description of its composition CHCl3 CH2Cl2 CCl4
CHCl3: this molecule contains 12.01 amu of carbon, 1,008 amu of hydrogen, and 106.35 amu of chlorine CH2CL2: 1 mole of this substance contains 12.01 g of carbon, 2.016 g of hydrogen, and 70.90 g of chlorine CCl4: 1 mole of this substance contains 1 mole of carbon and 4 moles of chlorine
which convention is used in the textbook for rounding off atomic masses based on the periodic table?
atomic masses are rounded to 4 sig figs
Which of the following net ionic equations correctly predicts the formation of an insoluble product? Select all that apply. a. 2NH₄⁺ (aq) + S²⁻ (aq) → (NH₄)₂ (s) b. Ba²⁺ (aq) + CO₃²⁻ (aq) →BaCO₃ (s) c. Ag⁺ (aq) + Br⁻ (aq) → AgBr (s) d. Na⁺ (aq) +Cl⁻ (aq) → NaCl (s)
b. Ba²⁺ (aq) + CO₃²⁻ (aq) →BaCO₃ (s) c. Ag⁺ (aq) + Br⁻ (aq) → AgBr (s)
the species reduced shows a
decrease in oxidation number
match each thermodynamic symbol with its correct definition:
deltaH rxn - The change in enthalpy for a given reaction deltaH o rxn - The enthalpy change of a reaction measured at the standard state deltaH o f - The enthalpy change when 1 mol of a compound forms from its elements in their standard states
Match each type of calorimeter with the thermochemical property that it measures
deltaH- constant pressure (coffee cup) calorimeter deltaE- bomb (constant volume) calorimeter (a bomb calorimeter is not at a constant pressure)
Note: a pure substance is defined as an element or a compound. Only the ΔH°f of an element in its standard state is 0 kJ/mol. Thus, substance would not be an adequate answer to this question.)
deltaT solid- positive (the solid will gain heat when it is placed in the water bath. deltaT solid is therefore positive) deltaT water bath- negative (the solid gains heat from the water bath, which therefore loses heat. deltaT water bath will be negative)
a reaction in which one or more precipitates form when the aqueous solutions of two ionic compounds are mixed is called a _____ displacement reaction, since both pairs of ions exchange partners. another name for this type of reaction is a ____ reaction
double-displacement, or metathesis
the movement of one or more ____ from one reactant to another is the key chemical event in an oxidation - ___ reaction, also called a ____
electrons; reduction; redox
By definition, the standard enthalpy of formation of a pure ______ in its standard state is equal to 0 kJ/mol.
element (Note: a pure substance is defined as an element or a compound. Only the ΔH°f of an element in its standard state is 0 kJ/mol. Thus, substance would not be an adequate answer to this question.)
match each term with its correct definition: empirical formula molecular formula structural formula
empirical: the simplest whole-number ratio of moles of element in a compound molecular: actual number of atoms of each element in a molecule structural: shows the relative placement and connection of atoms in a molecule
in a thermochemical equation, the ___ change is always written next to the balanced chemical equation
enthalpy
True or false: In order to balance the reaction of hydrogen gas (H2) with oxygen gas (O2) to form liquid water (H2O), a student adds a subscript of 2 after the oxygen in H2O. This is an acceptable method of balancing the above reaction.
false
the ____ heat capacity of a substance is the amount of heat needed to change the temperature of 1 mol of that substance by ____ K
molar; 1
the ____ mass of a substance is the mass per mole of its entities, where the term "entities" can describe ____, ions, molecules, or formula units
molar; atoms
each component in a mixture contributes a fraction to the total number of moles in the mixture. this fraction is called the ______ fraction of the component. in a mixture of gases, this fraction is proportional to the ______ pressure for each gas present
mole; partial
A chemical equation must be balanced. This means that the same _____ and _____ of atoms must appear on both sides of the equation.
number; type
a net ionic equation eliminates the _____ ions and shows the net chemical change taking place in a reaction
spectator
how does a gas exert pressure?
the moving gas particles strike each other and the walls of the container, exerting a force
Dalton's law of partial pressures states that for a mixture of gases, the _____ pressure is the ____ of the partial pressures of the individual gases (assume that the gases do not react with each other)
total; sum
A combustion reaction known to generate x kJ of heat is measured in a constant volume (bomb) calorimeter. If the calorimeter is observed to change from Ti oC to Tf oC, what is the heat capacity of the entire calorimeter (in kJ/K)?
x/Tf-Ti apparently it is easy to see that this is correct by checking the units. not all of us can be chem geniuses damn
