Q: A reaction in a supergiant star fuses two $$^{12}C $$nuclei to form $$^{23}Na $$and $$^1H. $$Given the atomic masses: $$^{12}C = 12.0000 $$amu, $$^{23}Na = 22.989767 $$amu, $$^1H = 1.007825 $$amu, calculate the energy released per mole of hydrogen formed. (1 amu = $$931.5$$ MeV, $$1 eV$$ = $$1.602 \times 10$$^{-19}$$ J, N_A = 6.022$$ \times $$10^{23}$$ mol$$^{-1})$$

2.16 \times $$10^{8}$$ \text{ kJ}

Question 1

Which of the following best describes the hybridization of the central atom in the ICl$$_2^-$$ ion, and what is the predicted molecular geometry according to VSEPR theory?

Accepted Answer

sp$$^3d$$, linear

Question 2

A sample contains 144 atoms of $$^{179}Au$$, which has a half-life of 7.5 seconds. Approximately how many such atoms were present 30 seconds earlier?

Accepted Answer

2304

Question 3

Which of the following elements has the smallest atomic radius?

Accepted Answer

Ar

Question 4

Which of the following molecules has no net dipole moment?

Accepted Answer

TeO$$_3$$

Question 5

Which of the following statements about molecular orbital (MO) theory is incorrect?

Accepted Answer

In a stable molecule having an even number of electrons, all electrons must be paired.

Question 6

The unusually high melting point of ammonia (NH$$_3) is $$primarily due to which type of intermolecular force?

Accepted Answer

Hydrogen bonding

Question 7

Which of the following correctly represents the process involved in the electron affinity of an element X?

Accepted Answer

X(g) + e^- \rightarrow X^-(g)

Question 8

How many resonance structures are possible for the nitrate ion, NO$$_3^-$$?

Accepted Answer

3

Question 9

Which of the following elements is the least electronegative?

Accepted Answer

Sr

Question 10

What is the molecular shape of ClF$$_4^- as $$predicted by VSEPR theory?

Accepted Answer

Square planar

Question 11

A reaction in a supergiant star fuses two $$^{12}C $$nuclei to form $$^{23}Na $$and $$^1H. $$Given the atomic masses: $$^{12}C = 12.0000 $$amu, $$^{23}Na = 22.989767 $$amu, $$^1H = 1.007825 $$amu, calculate the energy released per mole of hydrogen formed. (1 amu = $$931.5$$ MeV, $$1 eV$$ = $$1.602 	imes 10$$^{-19}$$ J, N_A = 6.022$$ 	imes $$10^{23}$$ mol$$^{-1})$$

Accepted Answer

2.16 	imes $$10^{8}$$ 	ext{ kJ}

Question 12

Which of the following should have the highest boiling point?

Accepted Answer

CI$$_4$$

Question 13

According to valence bond theory, the triple bond in ethyne (acetylene, C$$_2H$_2) $$consists of:

Accepted Answer

One $$\sigma$$ bond and two $$\pi$$ bonds

Question 14

In the hemoglobin molecule, iron has 6 single bonds to surrounding atoms. What is the most likely geometry of these bonds to iron?

Accepted Answer

Octahedral

Question 15

Which of the following best describes the trend in atomic radii for a set of isoelectronic species: A$$^{2-}$$, B$$^-$$, C, D$$^+$$, E$$^{2+}$$?

Accepted Answer

A$$^{2-}$$ \u003e B$$^-$$ \u003e C \u003e D$$^+$$ \u003e E$$^{2+}$$

Question 16

Which of the following best explains why the electron cloud of a molecule is easily distorted?

Accepted Answer

High polarizability

Question 17

What is the ideal bond angle in GeCl$$_4 as $$predicted by VSEPR theory?

Accepted Answer

$$109^\circ$$

Question 18

Acetone can be converted to isopropyl alcohol by addition of hydrogen to the carbon–oxygen double bond. Given the following bond energies (in kJ/mol): C=O: 745, H–H: 432, C–H: 413, O–H: 467, C–C: 347, C–O: 358. What is the enthalpy of reaction?

Accepted Answer

$$-61 kJ$$

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