Q: Which of the following is the correct calculation for the percent composition of oxygen in water ($$\mathrm{H}_2\mathrm{O}$$)?

$$\frac{16.00}{18.02} \times 100\%$$

Question 1

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

Accepted Answer

Accuracy refers to how close measurements are to the true value, while precision refers to how close measurements are to each other.

Question 2

A student measures the mass of a sample three times and records the following values: 2.51 g, 2.53 g, and 2.52 g. The actual mass is 2.80 g. Which statement is correct?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Which of the following is the correct way to express the result of $$4.56 	imes 1.4$$ using the correct number of significant figures?

Accepted Answer

$$6.4$$

Question 4

Which equation correctly converts a temperature of $$25\ ^\circ\mathrm{C} to $$Kelvin?

Accepted Answer

$$K = 25 + 273.15$$

Question 5

Which of the following best describes a compound?

Accepted Answer

A substance composed of two or more elements chemically combined in fixed proportions.

Question 6

Which of the following is a chemical property?

Accepted Answer

Reactivity with oxygen

Question 7

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of water. How many moles of water does this sample contain?

Accepted Answer

$$0.50$$ mol

Question 8

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

$$\mathrm{CH}_2\mathrm{O}$$

Question 9

Which of the following best describes the difference between an atom and a molecule?

Accepted Answer

An atom is the smallest unit of an element, while a molecule is a group of atoms bonded together.

Question 10

Which of the following is the correct balanced equation for the combustion of methane ($$\mathrm{CH}_4) in $$oxygen?

Accepted Answer

$$\mathrm{CH}_4 + 2\mathrm{O}_2 \rightarrow \mathrm{CO}_2 + 2\mathrm{H}_2\mathrm{O}$$

Question 11

A student needs to prepare $$250 mL of a$$ $$0.10 M $$NaCl solution. How many grams of NaCl are required? ($$\mathrm{NaCl}$$ molar mass $$= 58.44 g/$$mol)

Accepted Answer

$$1.46 g$$

Question 12

Which of the following statements about mixtures is correct?

Accepted Answer

Mixtures can be separated into their components by physical means.

Question 13

Which of the following is a physical change?

Accepted Answer

Melting of ice

Question 14

Which of the following is the correct molar mass of glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$)?

Accepted Answer

$$180 g/$$mol

Question 15

Which of the following is the correct net ionic equation for the reaction between aqueous solutions of NaCl and AgNO$$_3$$?

Accepted Answer

$$\mathrm{Ag}^+ + \mathrm{Cl}^- \rightarrow \mathrm{AgCl}(s)$$

Question 16

A compound contains $$24.0 g of $$carbon, $$4.0 g of $$hydrogen, and $$32.0 g of $$oxygen. What is the empirical formula?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 17

Which of the following best describes the law of conservation of mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 18

Which of the following is the correct calculation for the percent composition of oxygen in water ($$\mathrm{H}_2\mathrm{O}$$)?

Accepted Answer

$$\frac{16.00}{18.02} 	imes 100\%$$

Question 19

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

General Chemistry: Review of Introductory Skills – Study Notes

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