Q: Using the standard curve in the second image, what is the estimated concentration (in mg/dL) of a solution with an absorbance of 0.4?

$$\displaystyle 16~\text{mg/dL}$$

Q: A student reads the thermometer in image (b) of the first figure. What is the correct temperature reading to the appropriate number of significant figures?

$$\displaystyle 8.00~^\circ\text{C}$$

Q: A solution is prepared by diluting 25.0 mL of 6.00 M HCl to a final volume of 250.0 mL. What is the final concentration of the solution?

$$\displaystyle 0.75~\text{M}$$

Q: Which of the following is the correct empirical formula for a compound containing 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

$$\displaystyle \text{CH}_2\text{O}$$

Q: A 20.0 g piece of iron (specific heat $$0.45~\text{J/g} \cdot ^\circ\text{C}) is $$heated to $$250~^\circ\text{C}$$ and placed in $$100~\text{mL} of $$water at $$18~^\circ\text{C} ($$assume density of water is $$1.00~\text{g/mL}$$ and specific heat is $$4.18~\text{J/g} \cdot ^\circ\text{C}). $$What is the final temperature of the system?

$$\displaystyle 21.0~^\circ\text{C}$$

Q: Which of the following is the correct balanced equation for the combustion of pentanol ($$\text{C}_5\text{H}_{11}\text{OH}$$)?

$$\displaystyle \text{C}_5\text{H}_{11}\text{OH} + 7.5\text{O}_2 \rightarrow 5\text{CO}_2 + 6\text{H}_2\text{O}$$

Question 1

Which of the following best describes the classification of matter in the image labeled (a) in the first figure, and what is the correct reading of the liquid volume to the appropriate number of significant figures?

Accepted Answer

The liquid is a pure substance; the volume is 71.5 mL.

Question 2

Using the standard curve in the second image, what is the estimated concentration (in mg/dL) of a solution with an absorbance of 0.4?

Accepted Answer

$$\displaystyle 16~	ext{mg/dL}$$

Question 3

Which of the following best describes the physical change occurring if the liquid in image (c) of the first figure is heated until it evaporates?

Accepted Answer

A physical change, because the state of matter changes but the composition remains the same.

Question 4

Which of the following statements about the Law of Conservation of Mass is best illustrated by the molecular diagrams in the third and fourth images?

Accepted Answer

The total mass of reactants equals the total mass of products, as shown by the unchanged number of atoms.

Question 5

A student reads the thermometer in image (b) of the first figure. What is the correct temperature reading to the appropriate number of significant figures?

Accepted Answer

$$\displaystyle 8.00~^\circ	ext{C}$$

Question 6

Which of the following best describes the type of chemical reaction when methane reacts with oxygen to form carbon dioxide and water?

Accepted Answer

Combustion reaction

Question 7

Given the balanced equation $$2	ext{H}_2 + 	ext{O}_2 ightarrow 2	ext{H}_2	ext{O}$$, which diagram (a, b, c, or d from the third and fourth images) represents a mixture with neither reactant in excess?

Accepted Answer

Diagram c

Question 8

A solution is prepared by diluting 25.0 mL of 6.00 M HCl to a final volume of 250.0 mL. What is the final concentration of the solution?

Accepted Answer

$$\displaystyle 0.75~	ext{M}$$

Question 9

Which of the following is the correct empirical formula for a compound containing 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

Accepted Answer

$$\displaystyle 	ext{CH}_2	ext{O}$$

Question 10

A 20.0 g piece of iron (specific heat $$0.45~	ext{J/g} \cdot ^\circ	ext{C}) is $$heated to $$250~^\circ	ext{C}$$ and placed in $$100~	ext{mL} of $$water at $$18~^\circ	ext{C} ($$assume density of water is $$1.00~	ext{g/mL}$$ and specific heat is $$4.18~	ext{J/g} \cdot ^\circ	ext{C}). $$What is the final temperature of the system?

Accepted Answer

$$\displaystyle 21.0~^\circ	ext{C}$$

Question 11

Which scientist is credited with discovering the electron using cathode ray tubes?

Accepted Answer

J.J. Thomson

Question 12

Which of the following is the correct balanced equation for the combustion of pentanol ($$	ext{C}_5	ext{H}_{11}	ext{OH}$$)?

Accepted Answer

$$\displaystyle 	ext{C}_5	ext{H}_{11}	ext{OH} + 7.5	ext{O}_2 ightarrow 5	ext{CO}_2 + 6	ext{H}_2	ext{O}$$

Question 13

Which of the following best describes the difference between precision and accuracy?

Accepted Answer

Precision refers to how close measurements are to each other; accuracy refers to how close measurements are to the true value.

Question 14

A hydrated ionic compound has the formula $$	ext{CuSO}_4 \cdot 5	ext{H}_2	ext{O}. $$What is the percent by mass of water in this compound?

Accepted Answer

$$\displaystyle 36.1\%$$

Question 15

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

$$\displaystyle \frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100\%$$

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