J-Lab Chem Sci Investigations

How many liters are equivalent to five milliliters?

0.005 L

A 0.500 L solution of 6 M HCl has to be made. How much 12 M HCl is needed?

0.250 L

According to the above data, which of the following represents the average density for sample X using the correct number of significant figures?

0.81 g/mL

The accepted value for the specific heat of aluminum is 0.897 Joules per gram•°C. Which of the following sets of specific heat values for aluminum, calculated from a prior experiment, has the greatest accuracy and precision?

0.896 J/g•°C, 0.899 J/g•°C, 0.896 J/g•°C

A student performed a series of titrations to find the concentration of an unknown acid. The results of the titrations are shown in the data table. What is the mean of this set of data?

0.984 M

How is 0.00124 expressed in proper scientific notation?

1.24 × 10-3

Which of these shows a volume of 1.25 liters expressed in milliliters?

1.25 × 10^3 mL

A student conducted an experiment and was interested in the mass of the product of the chemical reaction. Some results are shown above. What is the mass of the NaCl?

1.75 g

A student measured the mass of a small object and found it to be 56.0 grams. The object's mass is known to be 55.0 grams. What is the percent of error in the student's measurement?

1.8%

If a student needed to obtain 8.0 mL of a liquid for an experiment, the appropriate piece of laboratory equipment to use would be a -

10.0 mL graduated cylinder

Measurement 1: 5.2 g Measurement 2: 5.4 g Measurement 3: 3 g Measurement 4: 2.45 g These data show repeated measurements of the same object which has a known mass of 5.38 grams. Which measurement is most accurate?

2

Which of these is the percent of error in evaluating the molecular mass of a compound if the experimental value was 105.2 amu and the known value was 107.5 amu?

2.1%

The graph shows the rate of a certain reaction as a function of temperature. According to the graph, in order to double the rate of the reaction at 20°C, the temperature must be increased by approximately -

20°C

The volume of Object X is approximately -

25 mL

A student used the above ruler to measure the length of a nail. The length of this nail, according to the precision of the ruler, is -

3.75 cm

A student massed a piece of iron on a balance. The most sensitive beam was marked off in 0.1 g intervals. The student reported the iron's mass as 12.34 g. Which of the digits in the measurement is estimated?

4

How many significant digits are in 0.003450?

4

What is the volume of the water in this graduated cylinder?

4.39 mL

What is the percentage of aluminum in aluminum oxide (Al2O3)?

53%

The melting point of a white solid substance was determined in four repeated trials to be 56.0°C, 55.0°C, 57.5°C, 55.5°C. What temperature should be reported as the melting point as a result of these trials?

56.0

The mass of an object was recorded as 9.93 g, 9.90 g, and 10.02 g, using an electronic analytic balance. What is the average of these three masses expressed to the correct number of significant figures?

9.95

A chemical engineer for a fertilizer company is determining the most efficient way to produce ammonia. The engineer carries out the Haber reaction under four different conditions. According to these data, which procedure gave the greatest percent yield?

B

Students want to separate and compare the components of black ink and green ink. Which technique is the best for the students to use?

Chromatography

The figure shows an experimental setup used to separate the components of a colored ink sample. Which of the following describes this laboratory technique?

Chromatography

A student was instructed to carry out an experiment that illustrates the law of conservation of mass. The teacher indicated that the experiment should be carried out three times. The student plans to report the average of the three results. What can the student do to maximize the reliability of the data collected?

Conduct each trial using the same balance.

Which of these laboratory techniques is best to separate a solid from a liquid to recover the liquid?

Filtering

If a lab group were using hydrochloric acid to perform a substitution reaction, which precaution would not be a concern?

Flammability

What is the first step that should be taken when a caustic chemical gets into a person's eye?

Flush the affected area with water

Which of the following pieces of glassware can be used to measure the volume of a liquid with the greatest accuracy?

Graduated cylinder

Which of these is the proper method for using a thermometer to measure the temperature of liquid in a beaker?

Middle center

Which salt's solubility in water is least affected by temperature?

NaCl

A student measures the mass of a piece of copper three times and records the results in the following table: A student measures the mass of a piece of copper three times and records the results in the following table: The actual mass of the copper is 28.7 grams. Which of the following is demonstrated in the student's data?

Precision

If a student's hand is accidentally exposed to an acidic solution, what should be done?

Rinse the hand in running water.

After 1911, most scientists accepted the theory that the nucleus of an atom was very dense and very small and had a positive charge. What led scientists to accept this theory?

Rutherford did an experiment firing alpha particles at a thin piece of gold foil.

Four students each took three temperature readings of a sample of water. The actual temperature of the sample was 80.0°C. Which student's measurements were both accurate and precise?

Student 4

When examining the physical properties of an unknown substance, which of the following characteristics is unsafe to observe?

Taste

The following results of a scientific study on water were found in a chemistry handbook. What is the independent variable in the study?

Temperature

The graph shows the pressure of an ideal gas as a function of its volume. According to the graph, increasing the volume from 100 mL to 150 mL -

decreases the pressure by 80 kPa

Methyl mercury, found in some stream sediments, is highly toxic to animal life. Using the graphed results of the study shown, the best analysis of the data reveals that the methyl mercury concentration in the stream sediment is -

decreasing but reaches a maximum at the end of summer

Which graph best represents the above generalization?

downwards slope

To remove the sand first and then the salt from a mixture of sand and salt water, one combination of techniques you could use would be to first -

filter and then evaporate

For an experiment, 9.7 mL of HCl are needed. What is the best instrument to use for measuring this volume?

graduated cylinder

The table shows the measurements of the volume and the pressure of a portion of a gas at constant temperature. After graphing, the data reveals that the volume is -

inversely proportional to pressure

A student is given a container of potassium nitrate crystals. In order to determine the exact mass of the potassium nitrate using a triple beam balance, he must know the -

mass of the empty container and the mass of the filled container

Many reactions are taken to completion by heating the reaction mixture in a test tube. Each of the following would be a safe practice except -

placing a stopper in the test tube to prevent gas from escaping

A student spills a diluted acid solution on his hand. He should -

rinse it off with running water

A student uses a mortar and pestle to crush 1.0 g of marble chips and places them into a test tube. A whole 1.0 g marble chip is placed into a second test tube, and 5.0 mL of 6 M HCl is added to each test tube. The bubbling speed of the produced CO2 gas is noted. This experiment is designed to study the effect of the -

surface area of a reactant on reaction rate

To determine the density of corn syrup, a student poured 3.0 mL of the liquid into a 10.0 mL graduated cylinder and massed the cylinder and contents. He determined the density to be 10.5 g/cm3. The accepted value for the density of corn syrup is 1.38 g/cm3. The most probable cause of error was that -

the mass of the cylinder was included in the density formula

A student wanted to calculate the formula for hydrated copper sulfate. After careful massing, she heated the compound to remove the water. She calculated the formula to be CuSO4 • 4H2O. the actual formula was CuSO4 • 5H2O. What was the most likely source of analytical error in the student's experiment?

The water was not completely evaporated from the compound.

Which of the following best describes why an experiment should be repeated?

To verify the observed results

A student conducted an experiment to study the effects of temperature on this chemical reaction. The student's experimental conditions are shown below. Which of the following would improve the student's experimental design?

Use the same amount of catalyst in all trials

A student wants to study the effects of volume on gas pressure. During his experiment, he recorded the above data. How could he now study the effects of temperature on gas pressure?

Vary the temperature but keep the gas volume constant