Q: What is the percent composition by mass of carbon in glucose ($$\mathrm{C_6H_{12}O_6$}$$)? ($$\mathrm{M$$_{C_6H_{12}$$O_6$$}} = 180\ \mathrm{g/mol}$)

$$\frac{6 \times 12}{180} \times 100 = 40\%$$

Question 1

Which of the following statements best explains why the second ionization energy of sodium ($$\mathrm{Na}) is $$much higher than its first ionization energy?

Accepted Answer

The second electron is removed from a core shell, which is closer to the nucleus and more strongly attracted.

Question 2

Which of the following compounds is most likely to be ionic based on the elements involved?

Accepted Answer

NaCl

Question 3

According to Coulomb's Law, which factor most directly causes the energy of an ionic bond to decrease (become more negative) as the ions approach each other?

Accepted Answer

Decreasing the distance between ions ($$r)$$

Question 4

Which of the following best describes the role of the octet rule in determining the formula of magnesium chloride?

Accepted Answer

Magnesium loses two electrons, each chlorine gains one, resulting in $$\mathrm{$$MgCl_2$$}.$$

Question 5

Which of the following ions has the same electron configuration as neon ($$\mathrm{Ne}$$)?

Accepted Answer

$$\mathrm{Na^+}$$

Question 6

A sample contains 18.0 g of water ($$\mathrm{H_2O}). $$What is the number of moles of water in the sample? ($$\mathrm{M_{H_2O}} = 18.0\ \mathrm{g/mol})$$

Accepted Answer

$$1.0$$ mol

Question 7

Which of the following molecules is expected to be polar based on its shape and bond polarities?

Accepted Answer

NH$$_3 ($$trigonal pyramidal)

Question 8

Which of the following best describes the difference between a sigma ($$\sigma) $$bond and a pi ($$\pi) $$bond?

Accepted Answer

A $$\sigma$$ bond is formed by head-on overlap of orbitals, while a $$\pi$$ bond is formed by side-to-side overlap.

Question 9

Which of the following statements about resonance is correct?

Accepted Answer

Resonance structures represent delocalized electrons, and the true structure is a hybrid of all resonance forms.

Question 10

Which of the following best explains why ozone ($$\mathrm{O_3$}) $$can absorb UV-B radiation while oxygen ($$\mathrm{O_2$}) $$cannot?

Accepted Answer

Ozone has resonance structures that allow electron delocalization, enabling absorption of UV-B.

Question 11

Which of the following is the correct formula for ammonium sulfate?

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Question 12

What is the percent composition by mass of carbon in glucose ($$\mathrm{C_6H_{12}O_6$}$$)? ($$\mathrm{M$$_{C_6H_{12}$$O_6$$}} = 180\ \mathrm{g/mol}$)

Accepted Answer

$$\frac{6 	imes 12}{180} 	imes 100 = 40\%$$

Question 13

Given a compound with a mass percent composition of 40% carbon, 6.7% hydrogen, and 53.3% oxygen, what is its empirical formula?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 14

Which of the following best describes the shape and bond angles of ammonia ($$\mathrm{NH_3$}) $$according to VSEPR theory?

Accepted Answer

Trigonal pyramidal, less than 109.5$$^\circ$$ due to lone pair repulsion

Question 15

Which hybridization is expected for the central carbon atom in ethene ($$\mathrm{C_2H_4}$$)?

Accepted Answer

$$\mathrm{sp^2$}$$

Question 16

Which of the following statements about molecular orbital theory is correct?

Accepted Answer

Bonding orbitals build electron density between nuclei, while antibonding orbitals have a node between nuclei.

Question 17

Why is $$\mathrm{H_2$} a $$stable molecule while $$\mathrm{He_2$} is $$not, according to molecular orbital theory?

Accepted Answer

$$\mathrm{He_2$}$$ has equal numbers of electrons in bonding and antibonding orbitals, resulting in no net bond.

Question 18

Which of the following best describes the energy change when a chemical bond forms?

Accepted Answer

Bond formation is an exothermic process because energy is released.

Question 19

Which of the following is the correct name for $$\mathrm{$$FeCl_3$$}$$ according to nomenclature rules?

Accepted Answer

Iron(III) chloride

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