ap chem midterm

the oxidation number of N in Ca(NO3)2 is a- +2 b- +3 c- +4 d- +5

+5

What is the enthalpy change for the following reaction? Cs2 + 3 O2 --> CO2 + 2 SO2 CS2= + 88 kj/mol CO2 = -394 kJ/mol SO2 = -297 kJ/mol a- -900 b- -779 c- -603 d- -1076

-1076 kJ

how many moles of barium sulfide, BaS, will form when 60 mL of 1 M BaNO32 are mixed with 25 mL of .8 M K2S solution to form a barium sulfide solid ?

.020 mol

a precipitation reaction is caused by mixing 100 mL of .25 M K2Cr2O7 with 100 mL of .25 M Pb(NO3)2 solution. when the precipitate forms, it is filtered from te mixture. how many moles of solid product are formed? a- .010 b- .025 c- .050 d- .25

.025 mol

which pair of samples contains the same number of oxygen atoms in each compound? a- .10 mol Pe2O3 and .5 mol BaO b- .20 mol Br2O and .2 mol HBrO c- .10 mol Na2O and .1 mol Na2SO4 d- .20 mol Ba(OH)2 and .20 mol H2SO4

.20 mol Br2O and .2 mol HBrO

Fe(s) + 2HCl ----> FeCl2 + H2 when a student adds 30 ml of 1M HCl to .56 g of powdered Fe, a reaction occurs according to the equation above. WHen the reaction is complete at 273K and 1 atm which of the following is true ? a- HCl is in excess, and .1 mol of HCl remains unreacted b- HCl is in excess, and .020 mol of HCl remains unreacted c- .015 mol of FeCl2 has been produced d- .22 L of H2 has been produced

.22 L of H2 has been produced

a precipitation reaction is caused by mixing 100 mL of .25 M K2Cr2O7 with 100 mL of .25 M Pb(NO3)2 solution. when the precipitate forms, it is filtered from te mixture. what is the concentration of nitrate anion in the reaction mixture after filtration? a- 0 b- .1 c- .25 d- .50

.25 M

how many moles of CaCl2 should be added to 1 L of .2 M BaCl2 solution to increase the chloride concentration to 1 M ? a- .20 b- .30 c- .40 d- .60

.3

a mixture of .4 mole of He gas and .5 mole of N2 gas exerts a total pressure of .9 atm at 25 oC. what is the partial pressure of the He gas? a- .36 b- .40 c- .45 d- .81

.36 atm

Exactly 174.4 J will raise the temperature of 10 g of a metal from 25 oC to 60 oC. WHat is the specific heat capacity of the metal? a- 2.01 b- .498 c- 17.7 d- 41.7 e- none of these

.498 J/g oC

2 ZnS + 3 O2 --> 2 ZnO + 2 SO2 how many moles of ZnO are produced when 32 g of oxygen is allowed to react with an excess of ZnS? a- .67 b- 1.0 c- 1.3 d- 2.0

.67

Sucrose (C12H22O11) has a molar mass of 342 g/mol. how many atoms of carbon are there in 684 g of sucrose? a- 6.02 x 10 ^ 23 b- 1.45 x 10 -25 atoms c- 1.2 x 10 ^ 24 d- 3.01 x 10 ^ 23

1.45 x 10 -25 atoms

?CH4 + ?O2 --> ?CO2 + ?H2O how many moles of which reactant remains after the reaction mixture that containing 32 g each Ch4 and O2? a- neither reactant remains b- 1.5 mol CH4 remains c- 1.0 mol O2 remains d- 2.0 mol CH4 remains

1.5 mol CH4 remains

which expression gives the mass percent of carbon in methnoic acid HCOOH? a- 2/46 x 100 b- 12/46 x 100 c- 16/46 x100 d- 12/29 x 100

12/46 x 100

what volume of 10.0 M NaOH must be used to prepare 500 ML of a 2.5 M solution? a- 125 b- 200 c- 250 d- 12.5

125 mL

how much heat is required to raise the temperature of 5.99 g sample of iron (Specific heat = .450 j/goC) from 25 oC to 79.8 oC? a- 2.64 b- 328 c- 729 d- 884 e- 148

148 J

hydrogen reacts with oxygen to form only water. if 16 grams of hydrogen is mixed with 16 grams of oxygen, how much water can form? a- .5 b- 8 c- 18 d- 72

18 grams

Of energy, work, enthalpy, and heat, how many are state functions? a- 0 b- 1 c- 2 d- 3 e- 4

2

C2H5OH (l) + 3O2 (g) -> 2CO2 (g) + 3H2O (l) change H= -1.37 x 10 *3 1. the reaction is endothermic 2. the reacation is exothermic 3. the enthalpy term would be different if the water formed was gaseous which are true? a- 1 b- 2 c- 3 d- 1 and 2 e- 2 and 3

2 and 3

PCl5 --> PCl3 + Cl2 (PCl5) P total = 1 atm (PCl5, PCl3, Cl2) P total= 1.40 atm if the decomposition reaction were to go to completion the total pressure in the container would be a- 1.4 b- 2 c- 2.8 d- 3.0

2 atm

2 Al + 3O2 --> 2 Al2O3 which expression approximates the volume of O2 consumed, measured at stp, when 55 g Al reacts completely with excess O2? a- 2 x 1.5 x 22.4 b- .5 x 1.5 x 22.4 c- 2 x .6 x 22.4 d- .5 x .6 x 22.4

2 x 1.5 x 22.4

the density of a mystery gas is 2.0 g/L what is the molar mass of this gas? a- 2 x 22.4 b - 22.4/2 c - 2/22.4 d- 2 x 24.5

2.0 x 22.4

When 4 L of He, 6 L of N2 and 10 L of Ar, all at 0 C and 1 atm, are pumped into an evacuated 8 L rigid container, the final pressure in the container at 0 is a- .5 b- 1 c- 2.5 d- 4.0

2.5 atm

how many moles of electrons are transferred between the substance being oxidized and the substance being reduced in the reaction 4 NH3 + 5 O2 --> 4 NO + 6 H2O a- 5 b- 10 c- 16 d- 20

20

C3H8 + 4 Cl2 --> C3H4Cl4 + 4 HCl a 6.0 mol sample of C3H8 and a 20 mol sample of Cl2 are placed in a previously evacuated vessel where they react according to the equation. after one of the reactants has been totally consumed, how many moles of HCl have been produced? a- 4 mol b- 8 mol c- 20 mol d- 24 mol

20 mol

how may grams of chromium are in 58.5 g of K2Cr2O7 (molar mass = 294 g/mol)

20.8 g of Cr

2 C2H2 + 7 O2 → 4 CO2 + 6 H2O what minimum volume of oxygen will be required to completely react with 6 liters of C2H6 a- 21.0 L b- 14 L c- 6 L d- 3.5 L

21.0 L

what is the percent mass nitrogen in sodium cyanide (NaCN)

28.57 %

approximately how long did it take for 75 percent of the initial amount of C25H30N3+ to react?

300s

Methane reacts with oxygen to form carbon dioxide and water (CH4 + 2O2 --> CO2 + 2H2O) if 72 g of water form how much methane mist have reacted a- 16 g b- 32g c- 36g d- 84g

32 g

how many mL of .250 M Ba(NO3)2 solution are required to precipitate all the sulfate anions from 50 mL of .2 M H2SO4 solution? a- 2.5 mL b- 40.0 mL c- 50 mL d- 62.5 mL

40.0 mL

when 16 g of methane (Ch4) and 32 g of oxygen reacted to produce carbon dioxide and water, 11 g of carbon dioxide was oroduced. calculate the percent yield of carbon dioxide in this equation

50%

under which of the following conditions of temperature and pressure will H2 gas be expected to behave most like an ideal gas? a- 50 K and .1 atm b- 50 K and 5.0 atm c- 500 K and .1 atm d- 500 K and 50 atm

500 K and .1 atm

2 Mg + O2 --> 2 MgO what mass of MgO is produced when .15 mole of magnesium reacts with excess oxygen a- 3 b- 3.6 c- 6.0 d- 12.0

6.0 g

C2H5OH (l) + 3 O2 (g) --> 2CO2 (g) + 3H20 (l) chnage H= -1.37x 10 *3 when a 23.2 g sample of ethyl alcohol (molar mass= 46.07) is burned, how much energy is released as heat? a- .504 b- .690 c- 6.9 x 10 ^ 2 d- 3.18 x 10 ^ 4 e- 1.99

6.90 x 10 ^ 2 kJ

which of the following solutions contains the largest number of ions? a- 500 Ml of .1 M FeCL3 b- 700 mL of .2 M NaOh c- 400 mL of .1 M Al(NO3)3 d- 600 mL of .2 M AlCl3

600 mL of .2 M AlCl3

a 18.2 g piece of aluminum (molar heat capacity= 24.03) is heated to 82.4 oC and dropped into a calorimeter container water (specific heat capacity= 4.18) initially at 22.3 oC. the final temperature of the water is 25 oC. calculate the mass of th water in the calorimeter. a- 82.4 b- 2.22 c- 2.49 d- 930

82.4 g

Aluminum reacts with sulfuric acid to produce aluminum sulfate and hydrogen gas. Give the sum of all coefficicients for this balanced chemical expression a- 5 b- 6 c- 9 d- 12

9

a 23 g sample of a compound contains 12 g of C, 3 g of H, and 8 g of O. which is the empirical formula a- CH3O b- C2H6O c- C3H9O2 d- C4H12O2

C2H6O

the density of a mystery gas is 2.0 g/L what is most likely the formula of this mystery gas? a- Ne b- CH4 c- CO d- C3H8

C3H8

complete combustion of a sample of hydrocarbon in excess oxygen produces equimolar quantities of carbon dioxide and water. which of the following could be the molecular formula of the compound? a- C2H2 b- C2H6 c- C4H8 d- C6H6

C4H8

A sample of a compound that contains only the elements C, H, and N is completely burned in O2 to produce 44.0 g of CO2, 45g of H2O, and some NO2. A possible empirical formula of the compound is a- CH2N b- CH5N c- C2H5N d- C3H3N2

CH5N

solution of CaCl2 and Na2CO3 are mixed and a precipitate is formed. what is the net ionic equation for the reaction a- CO3 -2 + Ca +2 --> CaCO3 b- 2 Cl- + 2 Na + --> NaCl c- CO3- + Ca +2 + 2 Cl- + 2 Na --> CaCO3 + 2NaCl

CO3 -2 + Ca +2 --> CaCO3

Cl2 and F2 combine to form a gaseous product; one volume of Cl2 reacts with three volumes of F2 yielding two volumes of product. Assuming constant conditions of temperature and pressure, what is the formula of the product? a- Cl2F2 b- ClF2 c- Cl2F d- ClF3

ClF3

Analysis of a sample of an oxide of chromium is reported as 26g of chromium and 12 g of oxygen. From this data determine the empirical ofrmula of this compound a- CrO b- Cr2O3 c- CrO3 d- Cr4O6

Cr2O3

which of the following does NOT have a standard enthalpy of formation equal to zero? a- F2 (g) b- Al (s) c- H2O (l) d- H2 (g) e- they all have it

H2O (l)

Which of the following will produce a solid closest to the tube? a- HCl and CH3NH2 b- HCl and NH3 c- HBr and CH3NH2 d- HBr and NH3

HCl and CH3NH2

which describes the resulting system when .40 moles of K2CO3 are added to 2.0 L of .6 M Ni(NO3)2 solution? a- a light green precipitate forms; excess carbonate anion is found in solution b- a light-green precipitate forms; excess nickel (ii) cation is found in solution c- a light green precipitate form; no excess reactants are found d- a white precipitate forms and no excess ions are found in solution

a light-green precipitate forms; excess nickel (ii) cation is found in solution

2 Na + Cl2 --> 2 NaCl 2 NaCl + Pb(NO3)2 --> PbCl2 + 2NaNO3 NaOH + HBr --> H2O + NaBr these are examples of

a redox reaction, a precipitation reaction, then an acid-base reaction

to gravimetrically analyze the silver content of a pice of jewelry made from an alloy of Ag and Cu, a student dissolves a small preweighed sample in HNO3. Ag+ and Cu+2 iones form in the solution. which should be the next step? a- centrifuging the solution to isolate the heavier ions b- evaporating the solution to recover dissolved nitrates c- adding enough base solution to bring th pH up to 7 d- adding a solution containing an anion that forms and insoluble salt with only one of the metal ions

adding a solution containing an anion that forms and insoluble salt with only one of the metal ions

2 H2O2 --> 2 H2O + O2 the exothermic process represented above is best classified as a

chemical change because covalent bonds are broken and new covalent bonds are formed

a real gas closely approaches the behavior of an ideal gas under conditions of

low pressure and high temperature

MnO4- + 5Fe +2 + 8 H+ --> Mn +2 + 5 Fe+3 + 4 H2O in the reaction above the nuber of MnO4- ions that react must be equal to which of the following? a- one fifth the number of Fe +2 ions that are consumed b- eight times the number of H+ ions that are consumed c- five times the number of Fe + ions that are produced d- one half the number of H2O molecules that are produced

one- fifth the number of Fe+2 ions that are consumed

a student is given a sample of a pure, white crystalline substance. which of the following would be most useful in providing data to determine if the substance is an ionic compound? a- examining the crystals of the substance under a microscope b- determining the density of the substance c- testing the electrical conductivity of the crystals d- testing the electrical conductivity of an aqueous solution of the substance

testing the electrical conductivity of an aqueous solution of the substance

a vessel contains Ar at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law? a- the molar mass of Ar is relatively large b- a significant numer of Ar2 moleculesform c- the attractive forces among Ar atoms cause them to collide with the walls of the container with less force d- the combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container

the combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container

Which of the following is the most likely explanation for the variance of the data point for the .600 M CuSO4 solution? a- the cuvette into which the .6 M solution was placed had some water droplets inside b- the cuvette into which the .6 M solution was placed was filled slightly more than the other cuvettes c- the wavelength setting was accidentally moved from that of maximum absorbance d- the cuvette used for the .6 M solution had not been wiped clean before being put in the spectrophotometer

the cuvette used for the .6 M solution had not been wiped clean before being put in the spectrophotometer

a sample of N2 gas is heated from 200 K to 400K in a rigid container. which of the following does NOT double? a- the average speed of the N2 molecules b- the pressure of the N2 molecules c- the density of the N2 gas d- the average kinetic energy of the N2 gas

the density of the N2 gas

Two metals of equal mass with different heat capacities are subjected to the same amount of heat. Which undergoes the smallest change in temperature? a- the metal with the higher heat capacity b- the metal with the lower heat capacity c- both undergo the same change in temperature d- you need to know the initial temp of the metals e - you need to know which metals you have

the metal with the higher heat capacity

A sample of a solid labeled as NaCl may be impure. a student analyzes the sample and determines that it contains 75 percent chlorine by mass. Pure NaCl contains 61 percent chlorine by mass. which of the following statements is consistent with the data? a- the sample contains only NaCl b- the sample contains NaCl and NaI c- the sample contains NaCl and KCl d- the sample contains NaCl and LiCl

the sample contains NaCl and LiCl

For a particular process q= -17 kJ and w= 21 kJ. which of the following statements is false? a- heat flows from the system to the surroundings b- the system does work on the surroundings c- change E = +4 kJ d- the process is exothermic e- none of the above is false

the system does work on the surroundings

During the course of the experiment, which of the following happens to the NO3- ions a- they are oxidized by the Cl- ions b- they are reduced to NO2- ions c- they are decomposed by reacting with M+ ions d- they remain dissolved in the filtrate solution

they remain dissolved in the filtrate solution

If a pure sample of an oxide of sulfur contains 40 percent sulfur and 60 percent oxygen by mass, then the empirical formula of the oxide is a- SO3 b- SO4 c- S2O6 d- S2O8

SO3

a .5 mol sample og H2 and a .5 mol sample of Ne are placed separately in two 10 L rigid containers at 25 oC. each container has a pinhole opening. which of the gases, He o Ne, will escape faster and why? a- He will escape faster because the He atoms are moving at a higher average speed than the Ne atoms b- Ne will escape faster because its initial pressure in the container is higher c- Ne will escape faster because the Ne atoms have a higher average kinetic energy than the He atoms d- Both gases will escape at the same rate because the atoms of both gases have the same average kinetic energy

He will escape faster because the He atoms are moving at a higher average speed than the Ne atoms

consider the equation Cl2 + 2 KI --> I2 + 2Kcl. which species is oxidized?

I-

Mass of unknown chloride, MCl - .74 g Mass of filter paper - .80 g Mass of filter paper AgCL precipitate - 2.23 g (Molar mass of AgCl is 143 g/mol) What is the identity of the metal chloride? (A) NaCl (B) KCl (C) CuCl (D) LiCl

KCl

molar mass of Na2O= 62 molar mass of MgO = 40.3 molar mass of K2O = 94.2 molar mass of CaO = 56.1 a 1 g sample of which of the following contains the greatest mass of oxygen ? a- Na2O b- MgO c-K2O d- CaO

MgO

a compound of nitrogen and oxygen is 63.64 % by mass nitrogen. what is the empirical formula of thos compound?

N2O

which of the following ions are likely to form a soluble sulfate in aq solution? a- Ba +2 b- Pb +2 c- NH4 + d- Ca +2

NH4+

2 K3PO4 + 3Mn --> Mn3(PO4)2 --> 6KNO3 a precipitate is formed when 1L of .2M potassium phosphate solution is mixed with .5L of 1.6 M manganese nitrate solution. after the reaction occurs, which list ranks the ions remaining in solution in order of decreasing concentration?

NO3- > K+ > Mn+2> PO4 -3

which would not forom a solid in an aqueous solution a- Ba 2+ and SO 4- b- Pb +2 and Br- c- Na + and SO4 -2 d- Pb +2 and S-2

Na + and SO4 -2

spectator ions are those which are in solution but do not react. identity any spectator ions for the reactions of sodium phosphate with calcium nitrate a- only PO 4 -3 b- Na + and PO4 -3 c- Na + and No3- d- Ca+2 and Po4-3

Na+ and NO3-