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In a laboratory activity, the density of a sample of vanadium is determined to be 6.9 g/cm3 at room temperature. What is the percent error for the determined value?*
The accepted value for the percent by mass of water in a hydrate is 36.0%. In a laboratory activity, a student determined the percent by mass of water in the hydrate to be 37.8%. What is the percent error for the student’s measured value?*
Which quantity is equal to 50 kilojoules?*
A student measures the mass and volume of a sample of copper at room temperature and 101.3 kPa. The mass is 48.9 grams and the volume is 5.00 cubic centimeters. The student calculates the density of the sample. What is the percent error of the student’s calculated density?*
Base your answers to questions 5 on the information below and on your knowledge of chemistry.
A company produces a colorless vinegar that is 5.0% HC2H3O2 in water. Using thymol blue as an indicator, a student titrates a 15.0-milliliter sample of the vinegar with 43.1 milliliters of a 0.30 M NaOH(aq) solution until the acid is neutralized.
The concentration of the base used in this titration is expressed to what number of significant figures?*
Base your answers to questions 6 on the information below.
In a titration, a few drops of an indicator are added to a flask containing 35.0 milliliters of HNO3(aq) of unknown concentration. After 30.0 milliliters of 0.15 M NaOH(aq) solution is slowly added to the flask, the indicator changes color, showing the acid is neutralized.
The volume of the NaOH(aq) solution is expressed to what number of significant figures?*
Base your answers to questions 7 on the information below and on your knowledge of chemistry.
The densities for two forms of carbon at room temperature are listed in the table below.
A student calculated the density of a sample of graphite to be 2.3 g/cm3. Show a numerical setup for calculating the student’s percent error for the density of graphite.*
Base your answers to questions 8 on the information below and on your knowledge of chemistry.
Three elements, represented by D, E, and Q, are located in Period 3. Some properties of these elements are listed in the table below. A student’s experimental result indicates that the density of element Q is 2.10 g/cm3, at room temperature and standard pressure.
Determine the percent error between the student’s experimental density and the accepted density of element Q.*
Base your answers to questions 9 on the information below.
The atomic number and corresponding atomic radius of the Period 3 elements are shown in the data table below.
On the grid below, mark an appropriate scale on the axis labeled “Atomic Radius (pm).”*
Base your answers to questions 10 on the information below and on your knowledge of chemistry.
During a laboratory activity, a student places 25.0 mL of HCl(aq) of unknown concentration into a flask. The student adds four drops of phenolphthalein to the solution in the flask. The solution is titrated with 0.150 M KOH(aq) until the solution appears faint pink. The volume of KOH(aq) added is 18.5 mL.
What number of significant figures is used to express the concentration of the KOH(aq)?*
Base your answers to questions 11 on the information below and on your knowledge of chemistry.
In a laboratory investigation, a student is given a sample that is a mixture of 3.0 grams of NaCl(s) and 4.0 grams of sand, which is mostly SiO2(s). The purpose of the investigation is to separate and recover the compounds in the sample. In the first step, the student places the sample in a 250-mL flask. Then, 50. grams of distilled water are added to the flask, and the contents are thoroughly stirred. The mixture in the flask is then filtered, using the equipment represented by the diagram below.
The student reports that 3.4 grams of NaCl(s) were recovered from the mixture. Show a numerical setup for calculating the student’s percent error.*
Base your answers to questions 12 on the information below and on your knowledge of chemistry.
A NaOH(aq) solution and an acid-base indicator are used to determine the molarity of an HCl(aq) solution. A 25.0-milliliter sample of the HCl(aq) is exactly neutralized by 15.0 milliliters of 0.20 M NaOH(aq).
Based on the data, the calculated molarity of the HCl(aq) solution should be expressed to what number of significant figures?*
Base your answers to questions 13 on the information below.
The active ingredient in the pain reliever aspirin is acetylsalicylic acid. This compound can be produced by reacting salicylic acid with acetic acid. The label of one aspirin bottle indicates that the accepted mass of acetylsalicylic acid in each tablet is 325 milligrams.
In a laboratory, an aspirin tablet is crushed and mixed with water to dissolve all of the acetylsalicylic acid. The measured pH of the resulting solution is 3.0.
The mass of acetylsalicylic acid in one aspirin tablet is determined to be 320. milligrams. Show a numerical setup for calculating the percent error for the mass of acetylsalicylic acid in this aspirin tablet.*
Base your answers to questions 14 on the information below and on your knowledge of chemistry.
In a laboratory activity, a student titrates a 20.0-milliliter sample of HCl(aq) using 0.025 M NaOH(aq). In one of the titration trials, 17.6 milliliters of the base solution exactly neutralizes the acid sample.
The concentration of the base is expressed to what number of significant figures?*
Base your answers to questions 15 on the information below and on your knowledge of chemistry.
The enclosed cabin of a submarine has a volume of 2.4 × 105 liters, a temperature of 312 K, and a pressure of 116 kPa. As people in the cabin breathe, carbon dioxide gas, CO2(g), can build up to unsafe levels. Air in the cabin becomes unsafe to breathe when the mass of CO2(g) in this cabin exceeds 2156 grams.
Convert the original air pressure in the cabin of the submarine to atmospheres.*
