Q: A coffee-cup calorimeter contains 100.0 g of water at 25.0°C. If 5.00 g of NaOH (molar mass = 40.0 g/mol) is dissolved and the temperature rises to 32.0°C, what is the approximate enthalpy change per mole of NaOH dissolved? (Assume $C_{water} = 4.18 \text{ J/g} \cdot \text{K}$ and no heat loss.)

$2.93 \times 10^4 \text{ J/mol}$

Q: Which of the following statements about the VSEPR theory is correct?

The shape of $\text{SF}_6$ is described as octahedral.

Question 1

Which of the following statements best describes the internal energy ($U$) of a system?

Accepted Answer

It is the sum of the potential and kinetic energies of the component molecules.

Question 2

Which one of the following is an endothermic process?

Accepted Answer

Melting solid ice

Question 3

Calculate the value of $\Delta H$ for the reaction below, given $\Delta H_f$ values:

$2	ext{H}_2(g) + O_2(g) ightarrow 2	ext{H}_2O(l)$

Given: $\Delta H_f(	ext{H}_2O(l)) = -286 	ext{ kJ/mol}$, $\Delta H_f(	ext{H}_2(g)) = 0$, $\Delta H_f(O_2(g)) = 0$

Accepted Answer

$-572 	ext{ kJ}$

Question 4

A coffee-cup calorimeter contains 100.0 g of water at 25.0°C. If 5.00 g of NaOH (molar mass = 40.0 g/mol) is dissolved and the temperature rises to 32.0°C, what is the approximate enthalpy change per mole of NaOH dissolved? (Assume $C_{water} = 4.18 	ext{ J/g} \cdot 	ext{K}$ and no heat loss.)

Accepted Answer

$2.93 	imes 10^4 	ext{ J/mol}$

Question 5

Which of the following statements about bond enthalpy is correct?

Accepted Answer

Bond breaking is always endothermic.

Question 6

Given the reaction: $	ext{Ti}(s) + O_2(g) ightarrow 	ext{TiO}_2(s)$, and the enthalpy of formation of $	ext{TiO}_2(s)$ is $-944 	ext{ kJ/mol}$, how much heat is released when 2.00 mol of titanium reacts completely?

Accepted Answer

$-1888 	ext{ kJ}$

Question 7

Which of the following molecules has the largest London dispersion forces?

Accepted Answer

$	ext{C}_6	ext{H}_{14}$

Question 8

What is the hybridization of the central carbon atom in $	ext{CO}_2$?

Accepted Answer

$sp$

Question 9

Which of the following best describes the molecular geometry of $	ext{NH}_3$?

Accepted Answer

Trigonal pyramidal

Question 10

For a process at constant volume, which of the following is true?

Accepted Answer

$q = \Delta E$ and $\Delta H = \Delta E$

Question 11

Which of the following molecules is polar?

Accepted Answer

$	ext{H}_2	ext{O}$

Question 12

What is the maximum number of bonds that can be formed between two atoms?

Accepted Answer

3

Question 13

Which of the following has the lowest boiling point?

Accepted Answer

$	ext{CH}_4$

Question 14

Which of the following molecules is most likely to exhibit hydrogen bonding?

Accepted Answer

$	ext{CH}_3	ext{NH}_2$

Question 15

Which of the following is the best Lewis structure for $	ext{OCl}_2$?

Accepted Answer

O with two single bonds to Cl, and two lone pairs on O

Question 16

Which of the following is an allowed resonance form for $	ext{NCO}^-$?

Accepted Answer

N triple bonded to C, single bonded to O, with a negative charge on O

Question 17

Which of the following statements about the VSEPR theory is correct?

Accepted Answer

The shape of $	ext{SF}_6$ is described as octahedral.

Question 18

Which of the following molecules would have bond angles of approximately $109.5^\circ$?

Accepted Answer

$	ext{CH}_4$ only

Question 19

Which of the following is true about the enthalpy change for an exothermic reaction?

Accepted Answer

The enthalpy of the products is lower than that of the reactants.

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