Q: An electron in a hydrogen atom drops from the 4th to the 2nd energy level, emitting a photon with a wavelength of $$650\ \mathrm{nm}. $$What is the energy of this photon?

$$3.06 \times 10$$^{-19}$$\ \mathrm{J}$$

Question 1

A 250 mL sample of sulfuric acid is titrated with 1.5 M sodium hydroxide. The equivalence point is reached with 226 mL of base. What is the molarity of the sulfuric acid? (Assume the reaction is $$\mathrm{H_2SO_4} + 2\mathrm{NaOH} \rightarrow \mathrm{Na_2SO_4} + 2\mathrm{H_2O})$$

Accepted Answer

$$0.678\ \mathrm{M}$$

Question 2

How much energy is required to heat 400 g of water from $$20^\circ\mathrm{C} to$$ $$100^\circ\mathrm{C}$$? (Specific heat capacity of water is $$4.18\ \mathrm{J/g^\circ C})$$

Accepted Answer

$$133,760\ \mathrm{J}$$

Question 3

Given the reaction $$2\mathrm{$$NaHCO_3$$} (aq) + \mathrm{H_2SO_4} (aq) \rightarrow \mathrm{Na_2SO_4} (aq) + 2\mathrm{CO_2$} (g) + 2\mathrm{H_2O} (l)$$, if 100 g of sodium bicarbonate reacts with excess sulfuric acid in a $$2\ \mathrm{m}^3$$ sealed container at $$100^\circ\mathrm{C}$$, what is the final pressure of the container?

Accepted Answer

$$0.018\ \mathrm{atm}$$

Question 4

A researcher mixes 100 g of sodium bicarbonate and 100 mL of 6 M sulfuric acid. What is the mass of water produced in the reaction $$2\mathrm{$$NaHCO_3$$} + \mathrm{H_2SO_4} \rightarrow \mathrm{Na_2SO_4} + 2\mathrm{CO_2$} + 2\mathrm{H_2O}$$?

Accepted Answer

$$21.42\ \mathrm{g}$$

Question 5

An electron in a hydrogen atom drops from the 4th to the 2nd energy level, emitting a photon with a wavelength of $$650\ \mathrm{nm}. $$What is the energy of this photon?

Accepted Answer

$$3.06 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 6

A gas has a volume of $$8.5\ \mathrm{L} at$$ $$52^\circ\mathrm{C}. If $$the temperature is raised to $$200^\circ\mathrm{C} at $$constant pressure, what is the new volume?

Accepted Answer

$$12.4\ \mathrm{L}$$

Question 7

A compound has the following mass composition: $$33.4\% C$$, $$5.55\% H$$, $$38.88\% N$$, $$22.22\% O$$, and a molar mass of $$360.1\ \mathrm{g/mol}. $$What is its empirical formula?

Accepted Answer

$$\mathrm{C_2H_4N_2O}$$

Question 8

A solution of silver nitrate is mixed with a solution of iron(II) sulfate. What is the net ionic equation for the reaction?

Accepted Answer

$$2\mathrm{Ag}^+ (aq) + \mathrm{SO_4$}^{2-} (aq) \rightarrow \mathrm{Ag_2SO_4} (s)$$

Question 9

If 3 moles of nitrogen gas and 3 moles of hydrogen gas are placed in a container and allowed to react to form ammonia ($$\mathrm{N_2$} + 3\mathrm{H_2$} \rightarrow 2\mathrm{NH_3$}$$), and each mole of gas exerts 1 atm, what is the final total pressure in the container?

Accepted Answer

$$4\ \mathrm{atm}$$

Question 10

A 10 g strip of copper at $$100^\circ\mathrm{C} is $$placed in 100 g of water at $$25^\circ\mathrm{C}. $$The final temperature is $$27^\circ\mathrm{C}. $$What is the specific heat capacity of copper?

Accepted Answer

$$1.15\ \mathrm{J/g^\circ C}$$

Question 11

What is the hybridization of a tetrahedral carbon atom?

Accepted Answer

$$\mathrm{sp^3$}$$

Question 12

A gas has a volume of $$10\ \mathrm{L}$$, a temperature of $$27^\circ\mathrm{C}$$, and a pressure of $$740\ \mathrm{torr}. $$The volume increases to $$15\ \mathrm{L}$$ and the pressure decreases to $$6\ \mathrm{psi}. $$What is the new temperature in Kelvin? ($$1\ \mathrm{atm} = 14.69\ \mathrm{psi} = 760\ \mathrm{torr})$$

Accepted Answer

$$184\ \mathrm{K}$$

Question 13

A gas mixture has a total pressure of $$875\ \mathrm{torr}. If $$the mole fraction of $$\mathrm{O_2$} is$$ $$0.35$$, what is the partial pressure of $$\mathrm{O_2$}$$?

Accepted Answer

$$306.25\ \mathrm{torr}$$

Question 14

When 10 g of octane ($$\mathrm{C_8H_{18}}) is $$combusted in a bomb calorimeter, how many grams of water are produced?

Accepted Answer

$$14.21\ \mathrm{g}$$

Question 15

A bomb calorimeter with a heat capacity of $$6\ \mathrm{kJ$$/^{\circ}$$C}$$ increases in temperature by $$30^\circ\mathrm{C}$$ after combusting 10 g of octane. What is the molar heat of combustion for octane?

Accepted Answer

$$2052\ \mathrm{kJ/mol}$$

Question 16

In the combustion of 10 g of octane in a bomb calorimeter with a constant volume of 1 L, the final temperature is $$130^\circ\mathrm{C}. $$What is the pressure of the carbon dioxide produced? (Assume ideal gas behavior and complete combustion.)

Accepted Answer

$$23.1\ \mathrm{atm}$$

Question 17

A compound has the empirical formula $$\mathrm{C_2H_4N_2O}$$ and a molar mass of $$360.1\ \mathrm{g/mol}. $$What is its molecular formula?

Accepted Answer

$$\mathrm{C$$_{10}$$H_{20}N$$_{10}$$O_5$$}$

Question 18

If the reaction $$2\mathrm{$$NaHCO_3$$} + \mathrm{H_2SO_4} \rightarrow \mathrm{Na_2SO_4} + 2\mathrm{CO_2$} + 2\mathrm{H_2O} is $$exothermic with $$\Delta H = -300\ \mathrm{kJ/mol}$$, and the system absorbs $$2000\ \mathrm{kJ} of $$work from the surroundings, what is the change in internal energy ($$\Delta E) if 0.59 $$mol of reaction occurs?

Accepted Answer

$$178\ \mathrm{J}$$

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