Q: A sample contains 18.0 g of water ($$\mathrm{H_2O}). $$How many molecules of water are present in the sample? (Molar mass of $$\mathrm{H_2O}$$ = $$18.0\ \mathrm{g/mol})$$

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

Question 1

Which of the following best describes the difference between an empirical formula and a molecular formula?

Accepted Answer

The empirical formula shows the simplest whole-number ratio of atoms in a compound, while the molecular formula shows the actual number of atoms in a molecule.

Question 2

Which of the following compounds is named correctly according to IUPAC rules?

Accepted Answer

NaCl: Sodium chloride

Question 3

A sample contains 18.0 g of water ($$\mathrm{H_2O}). $$How many molecules of water are present in the sample? (Molar mass of $$\mathrm{H_2O}$$ = $$18.0\ \mathrm{g/mol})$$

Accepted Answer

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

Question 4

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 5

Which of the following elements has the highest ionization energy?

Accepted Answer

Fluorine ($$\mathrm{F})$$

Question 6

Which of the following statements about metallic bonds is correct?

Accepted Answer

Metallic bonds involve a sea of delocalized electrons surrounding positive metal ions.

Question 7

Which bond is both the strongest and shortest among covalent single, double, and triple bonds?

Accepted Answer

Triple bond

Question 8

What is the mass percent of carbon in glucose ($$\mathrm{C_6H_{12}O_6$}$$)? (Molar mass: $$\mathrm{C_6H_{12}O_6$}$$ = $$180\ \mathrm{g/mol}$$; C = $$12.0\ \mathrm{g/mol})$$

Accepted Answer

$$40\%$$

Question 9

Which of the following best describes electronegativity?

Accepted Answer

The ability of an atom to attract electrons in a chemical bond.

Question 10

Which of the following is the correct electron configuration for the $$\mathrm{O$$^{2-}$$}$$ ion?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 11

Which of the following compounds has the greatest number of lone pairs on the central atom in its Lewis structure?

Accepted Answer

$$\mathrm{H_2O}$$

Question 12

Which of the following statements about ionic bonds is correct?

Accepted Answer

Ionic bonds are formed by the transfer of electrons from one atom to another.

Question 13

Which of the following is the correct formula for calcium phosphate, given the ions $$\mathrm{Ca$$^{2+}$$}$$ and $$\mathrm{PO_4$^{3-}}$$?

Accepted Answer

$$\mathrm{Ca_3$(PO_4$)_2}$$

Question 14

Which of the following atoms has the largest atomic radius?

Accepted Answer

Sodium ($$\mathrm{Na})$$

Question 15

A compound contains 52.2% carbon, 34.8% hydrogen, and 13.0% oxygen by mass. What is the empirical formula?

Accepted Answer

Question 16

Which of the following is the best Lewis structure for $$\mathrm{CO_2$}$$?

Accepted Answer

O=C=O with no lone pairs on carbon and two lone pairs on each oxygen

Question 17

Which of the following statements about bond energy is correct?

Accepted Answer

Bond energy is the energy required to break one mole of bonds in a substance.

Question 18

Which of the following trends is correct for atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases from left to right.

Question 19

Which of the following is the correct formal charge for the oxygen atom in the best Lewis structure of $$\mathrm{H_2O}$$?

Accepted Answer

0

Question 20

Which of the following statements about the periodic trend of metallic character is correct?

Accepted Answer

Metallic character decreases from left to right across a period.

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