Q: A sample contains 0.0314 moles of copper (Cu). What is the mass of copper in grams? (Molar mass of Cu = 63.55 g/mol)

$$0.0314 \times 63.55 = 1.996 g$$

Q: What is the molar mass of $$\mathrm{$$CaCO_3$$} ($$calcium carbonate)? (Atomic masses: Ca = 40.08, C = 12.01, O = 16.00)

$$40.08 + 12.01 + 3 \times 16.00 = 100.09 g/$$mol

Q: How many atoms are in 12.0000 grams of $$^{12}C$$?

$$6.02 \times 10$$^{23}$$ atoms

Question 1

Which law states that a chemical compound always contains exactly the same proportion of elements by mass, regardless of the source or method of preparation?

Accepted Answer

The Law of Constant Composition

Question 2

A sample of an oxide of nitrogen contains 1.00 mg N and 2.29 mg O. What is the mass ratio of oxygen to nitrogen in this compound?

Accepted Answer

$$\frac{2.29}{1.00} = 2.29$$

Question 3

Which experiment or technique is illustrated by the analysis of molecules in an exhaled breath to diagnose diseases or detect environmental exposure?

Accepted Answer

Mass Spectrometry

Question 4

According to Dalton’s Atomic Theory, which statement is FALSE?

Accepted Answer

Atoms are created and destroyed in chemical reactions.

Question 5

A compound contains 1.00 mg N and 1.14 mg O. Another contains 1.00 mg N and 2.29 mg O. Which law explains the existence of these two compounds?

Accepted Answer

The Law of Multiple Proportions

Question 6

Which of the following is the correct chemical formula for water?

Accepted Answer

$$\mathrm{H_2O}$$

Question 7

If 0.134 g of $$\mathrm{H_2$}$$ reacts with 1.066 g of $$\mathrm{O_2$} to $$form water, what is the total mass of water produced?

Accepted Answer

$$1.200 g$$

Question 8

Which subatomic particle has a charge of $$+1.602 	imes 10$$^{-19}$$ C and a mass of approximately 1.00727$ amu?

Accepted Answer

Proton

Question 9

A sample contains 0.0314 moles of copper (Cu). What is the mass of copper in grams? (Molar mass of Cu = 63.55 g/mol)

Accepted Answer

$$0.0314 	imes 63.55 = 1.996 g$$

Question 10

Which of the following best describes an isotope?

Accepted Answer

Atoms with the same number of protons but different numbers of neutrons

Question 11

What is the molar mass of $$\mathrm{$$CaCO_3$$} ($$calcium carbonate)? (Atomic masses: Ca = 40.08, C = 12.01, O = 16.00)

Accepted Answer

$$40.08 + 12.01 + 3 	imes 16.00 = 100.09 g/$$mol

Question 12

Which statement about the Law of Conservation of Mass is correct?

Accepted Answer

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

Question 13

A molecule contains 6 protons and 6 neutrons. What is its atomic mass in amu?

Accepted Answer

$$6 + 6 = 12$$ amu

Question 14

Which of the following is a correct example of a chemical symbol and its element?

Accepted Answer

Na for Sodium

Question 15

If the average atomic mass of boron is 10.811 amu, what does this value represent?

Accepted Answer

The weighted average of all naturally occurring isotopes of boron

Question 16

Which of the following is NOT a postulate of Dalton’s Atomic Theory?

Accepted Answer

Atoms can be converted into other elements by chemical reactions.

Question 17

How many atoms are in 12.0000 grams of $$^{12}C$$?

Accepted Answer

$$6.02 	imes 10$$^{23}$$ atoms

Question 18

Which of the following best describes a molecule?

Accepted Answer

A group of atoms bonded together

Question 19

What is the charge and mass of a neutron?

Accepted Answer

Charge: 0, Mass: 1.00866 amu

Question 20

Which of the following is a real-world application of the Law of Conservation of Mass?

Accepted Answer

Measuring the mass of reactants and products in a chemical reaction to confirm they are equal

Atoms, Molecules, and Ions: Laws of Chemical Combination

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