AP Chem 1-4

D

"The figure presents the graph of a line with the origin labeled O. The horizontal axis is labeled Volume, in milliliters, and the numbers 5 through 50, in increments of 5 are indicated. The vertical axis is labeled Temperature, in degrees Celsius, and the numbers 20 through 140, in increments of 20, are indicated. The line has data points along it. There are vertical gridlines at approximately 8 milliliters, 21.5 milliliters, 27.5 milliliters, and 42 milliliters. Between each vertical gridline the range is labeled. The labels are as follows: A, B, C, and D. The data of the line is as follows. Note that all values are approximate. The line begins in range A at 1 milliliter, 15 degrees Celsius and moves steeply upward and to the right. It reaches the point 8 milliliters, 99 degrees Celsius and moves horizontally to the right through range B. It reaches the point 23 milliliters, 99 degrees Celsius, in range C, and then moves upward and to the right. It reaches the point 27.5 milliliters, 125 degrees Celsius, and moves horizontally and to the right through range D. The line ends at 44 milliliters, 125 degrees Celsius." A student performed a fractional distillation of a mixture of two straight-chain hydrocarbons, C7H16 and C8H18. Using four clean, dry flasks, the student collected the distillate over the volume ranges (A, B, C, and D) shown in the graph above. Over what volume range should the student collect the distillate of the compound with the stronger intermolecular forces?

The mass of Mg and the mass of Cl in the sample

A 5.0g sample of MgCl2 may contain measurable amounts of other compounds as impurities. Which of the following quantities is (are) needed to determine that the sample is pure MgCl2 ?

3, 4, 6, 7

A sample of carbonate rock is a mixture of CaCO3 and MgCO3. The rock is analyzed in a laboratory, and the results are recorded in the table above. Which columns in the table provide all the information necessary to determine the mole ratio of Ca to Mg in the rock?

KBr<KCl<NaCl

A student has a 1g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample?

Which has the greater molar mass, X or Z?

A student has samples of two pure compounds, XClO3 and ZClO3, which contain unknown alkali metals X and Z. The student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of XCl and ZCl. The student measures the mass of the solid residue from each sample. Which of the following questions can be answered from the results of the experiment?

Which sample has the higher purity?

A student has two samples of NaCl, each one from a different source. Assume that the only potential contaminant in each sample is KCl. The student runs an experiment to determine the percent by mass of chlorine in each sample. From the results of this experiment alone, which of the following questions is most likely to be answered?

Pb2+(aq) + Br-aq --> PbBr2(s)

Equal volumes of 0.2⁢� solutions of lead(II) nitrate and potassium bromide are combined to form lead(II) bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?

0.0300 mol

How many moles of Na+ ions are in 100.mL of 0.100M Na3PO4(aq) ?

"There are 3 circles labeled N a with a positive one charge and 3 circles labeled N O 3 with a negative one charge. At the bottom of the box, there are 6 circles touching each other. 3 of the 6 circles are labeled A g with a positive one charge and 3 are labeled C l with a negative one charge, with the two types of circles alternating."

The diagrams above represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred?

Mo

Which of the following elements has the mass spectrum represented above?

The amount of OF2(g) produced is halved.

2F2(g)+2NaOH(aq)→OF2(g)+2NaF(aq)+H2O(l) A 2mol sample of F2(�) reacts with excess NaOH(��) according to the equation above. If the reaction is repeated with excess NaOH(��) but with 1 mol of F2(�), which of the following is correct?

The mass of Cl in each mixture

A student is given two 10g samples, each a mixture of only NaCl(s) and KCl(s) but in different proportions. Which of the following pieces of information could be used to determine which mixture has the higher proportion of KCl(s) ?

After the water has evaporated, the white crystals in the beaker have a mass of 20.0g.

A student mixes 20.0g of white KCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred?

"The figure presents a tube that is vertically positioned and with a stopcock and narrow tip at its lower end. An arrow indicates that fluid is moving from top to bottom in the tube, and then out through the narrow tip in a container. Two thin horizontal bands are visible at different heights in the tube."

A student obtains a liquid sample of green food coloring that is known to contain a mixture of two solid pigments, one blue and one yellow, dissolved in an aqueous solution of ethanol. Which of the following laboratory setups is most appropriate for the student to use in order to separate and collect a substantial sample of each of the two pigments?

Molar mass of the compound, mass of the sample

A student obtains a sample of a pure solid compound. In addition to Avogadro's number, which of the following must the student know in order to determine how many molecules are in the sample?

0.200M

A student uses visible spectrophotometry to determine the concentration of CoCl2(��) in a sample solution. First the student prepares a set of CoCl2(��) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. The original solution used to make the solutions for the standard curve was prepared by dissolving 2.60g of CoCl2 (molar mass 130.g/mol) in enough water to make 100.mL of solution. What is the molar concentration of the solution?

The resulting solution would contain a precipitate.

A student was asked to formulate a hypothesis about what would happen if 100.mL of 0.1M NaOH(aq) at 25°C was combined with 100.mL of 0.1M MgCl2(aq) at 25°C. Which of the following hypotheses indicates that the student thought a chemical change would occur?

A cube of metal was changed into a flat sheet of metal.

A student was studying physical and chemical changes. The student carried out some procedures in the laboratory and recorded observations. For one of the procedures, the student concluded that a physical change took place, but not a chemical change. Which of the following could have been the results of the procedure?

2

Al(�)→Al3+(��)+3�− Zn2+(��)+2�−→Zn(�) The half-reactions for the oxidation-reduction reaction between Al(�) and Zn2+(��) are represented above. Based on the half-reactions, what is the coefficient for Al(�) if the equation for the oxidation-reduction reaction is balanced with the smallest whole-number coefficients? A

The initial amount of C6H12O6 in the container must have been 0.10mol.

C6H12O6+6O2→6CO2+6H2O The reaction between C6H12O6 and O2 is represented by the balanced equation above. In an experiment, 0.30mol of CO2 was produced from the reaction of 0.05mol of C6H12O6 with excess O2. The reaction was repeated at the same temperature and in the same container, but this time 0.60mol of CO2 was produced. Which of the following must be true?

Oxidation Half-reaction Cu(�)→Cu2+(��)+2�− Reduction Half-reaction Ag+(��)+�−→Ag(�)

Cu(�)+2AgNO3(��)→Cu(NO3)2(��)+2Ag(�) The reaction between solid copper and aqueous silver nitrate produces solid silver and a blue solution, as represented by the balanced equation shown above. Based on the balanced equation, which of the following identifies the oxidation and reduction half-reactions?

H2O(l) and Cl-(aq)

HCl(aq)+H2O(l)→H3O+(aq)+Cl−(aq) For the dissolution of HCl in water represented above, which of the following pairs includes the Brønsted-Lowry bases?

The temperature of the reaction mixture increases.

HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l) A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place?

0.555g

How many grams of CaCl2 (molar mass =111g/mol) are needed to prepare 100.mL of 0.100M Cl−(aq) ions?

Oxidation-reduction, because I2 is reduced.

I2(��)+C6H8O6(��)→C6H6O6(��)+2I−(��)+2H+(��) The compound C6H8O6 reacts with I2 according to the reaction represented by the equation above. The reaction is correctly classified as which of the following types?

The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

Mass of empty crucible 12.0g Mass of crucible and sample before heating 14.4g Mass of crucible and sample after heating 16.0g A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?

Using twice the volume of MgCl2(aq) and twice the volume of NaOH(aq)

MgCl2(aq)+2NaOH(aq)→2NaCl(aq)+Mg(OH)2(s) A 100mL sample of 0.1�MgCl2(��) and a 100mL sample of 0.2�NaOH(��) were combined, and Mg(OH)2(�) precipitated, as shown by the equation above. If the experiment is repeated using solutions of the same molarity, which of the following changes in volume will double the amount of Mg(OH)2(�) produced?

NH4+(aq) is a stronger acid than H2O(l) is.

NH4+(aq)+OH−(aq)→NH3(aq)+H2O(l) When 0.20 M NH4Cl(aq) and 0.20 M NaOH(aq) are mixed, the reaction represented by the equation above occurs and a strong smell of ammonia, NH3, is observed. Based on this information, which of the following statements is true?

2Ag+(aq) + Ni(s) --> 2Ag(s) + Ni2+(aq)

Ni(�)→Ni2+(��)+2�− Ag+(��)+�−→Ag(�) Which of the following is the balanced net ionic equation for an oxidation-reduction reaction between Ag+(��) and Ni(�) based on the half-reactions represented above?

Decrease the percentage of ethyl acetate in the solvent.

The diagram above shows a thin-layer chromatogram of a mixture of products from a chemical reaction. The separation was performed using 50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatogram and the information about solvents in the table above, which of the following would be the best way to decrease the distance that the products travel up the plate?

Mg with 14 neutrons

The mass spectrum of a sample of a pure element is shown above. Based on the data, the peak at 26amu represents an isotope of which of the following elements?

Line at 121 and 123

The mass spectrum of the element Sb is most likely represented by which of the following?

One with 2 H's and one with 3 H's

The particle diagram above represents an aqueous solution of a weak monoprotic acid. The white circles represent H atoms. Which of the following shows the species that act as a Brønsted-Lowry base and its conjugate acid, in that order, in the solution?

Sr2+(aq) + SO4^2(aq) --> SrSO4 (s)

The reaction between aqueous strontium chloride (SrCl2) and aqueous potassium sulfate (K2SO4) forms a precipitate of strontium sulfate (SrSO4). Which of the following represents the net ionic equation for the reaction?

What is the formula unit of each compound?

Two different ionic compounds each contain only copper and chlorine. Both compounds are powders, one white and one brown. An elemental analysis is performed on each powder. Which of the following questions about the compounds is most likely to be answered by the results of the analysis?

Measuring the electrical conductivities of X and the mixture of water and X

Water Clear, colorless liquid 100.0°C 1.00g/mL X White, crystalline solid 1935.5°C 2.15g/mL Mixture of water +X Clear, colorless liquid 101.6°C 1.08g/mL The table above summarizes data given to a student to evaluate the type of change that took place when substance X was mixed with water. The student claimed that the data did not provide enough evidence to determine whether a chemical or physical change took place and that additional tests were needed. Which of the following identifies the best way to gather evidence to support the type of change that occurred when water and X were mixed?

Oxidation-reduction, because H2(�) is oxidized.

When C2H4(�) reacts with H2(�), the compound C2H6(�) is produced, as represented by the equation above. The reaction is correctly classified as which of the following types?

F-(aq) + H+(aq) --> HF(aq)

Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid?

2.0g / 20.18g/mol (6.0 x 10^23 particles/mol)

Which of the following numerical expressions gives the number of particles in 2.0g of Ne?