Q: Convert 4.89 mg to grams. Which of the following is correct?

$$4.89 \times 10$$^{-3}$$ g = 0.00489 g$

Q: What is the percent composition by mass of sulfur in H$$_2SO$_3$$? (H = 1.01 g/mol, S = 32.07 g/mol, O = 16.00 g/mol)

$$\frac{32.07}{82.09} \times 100\% = 39.07\%$$

Q: How many grams of sulfur are in 4.58 g of H$$_2SO$_3$$? (Use your answer from the previous question: 39.07%)

$$4.58 \times 0.3907 = 1.79 g$$

Q: Given the reaction $$3 \text{H}_2 + \text{N}_2 \rightarrow 2 \text{NH}_3$$, how many moles of H$$_2$$ are needed to produce 3.40 g of NH$$_3$$? (Molar mass NH$$_3 = 17.03 g/$$mol)

$$3.40 \text{ g} \times \frac{1 \text{ mol}}{17.03 \text{ g}} \times \frac{3 \text{ mol H}_2}{2 \text{ mol NH}_3} = 0.300 \text{ mol}$$

Q: What is the molarity of a solution containing 32.5 g of NaCl dissolved in 500. mL of solution? (Molar mass NaCl = 58.44 g/mol)

$$\frac{32.5 \text{ g}}{58.44 \text{ g/mol}} = 0.556 \text{ mol}; \frac{0.556 \text{ mol}}{0.500 \text{ L}} = 1.11 \text{ M}$$

Q: How much of a 3.0 M HCl stock solution is needed to make 25 mL of 0.10 M HCl?

$$M_1V_1 = M_2V_2 \rightarrow V_1$ = \frac{0.10 \times 25}{3.0} = 0.83 mL$$

Question 1

Which of the following is a chemical change?

Accepted Answer

Iron rusts over time and exposure to moisture in the air

Question 2

Convert 4.89 mg to grams. Which of the following is correct?

Accepted Answer

$$4.89 	imes 10$$^{-3}$$ g = 0.00489 g$

Question 3

How many significant figures are in the value 0.000480?

Accepted Answer

3

Question 4

Which of the following is the correct scientific notation for 0.000340?

Accepted Answer

$$3.40 	imes 10$$^{-4}$$

Question 5

What is the correct name for the compound FeCl$$_2$$?

Accepted Answer

Iron(II) chloride

Question 6

What is the percent composition by mass of sulfur in H$$_2SO$_3$$? (H = 1.01 g/mol, S = 32.07 g/mol, O = 16.00 g/mol)

Accepted Answer

$$\frac{32.07}{82.09} 	imes 100\% = 39.07\%$$

Question 7

How many grams of sulfur are in 4.58 g of H$$_2SO$_3$$? (Use your answer from the previous question: 39.07%)

Accepted Answer

$$4.58 	imes 0.3907 = 1.79 g$$

Question 8

An unknown compound contains 36.86% nitrogen and 63.14% oxygen by mass. What is its empirical formula?

Accepted Answer

NO$$_2$$

Question 9

Given the reaction $$3 	ext{H}_2 + 	ext{N}_2 ightarrow 2 	ext{NH}_3$$, how many moles of H$$_2$$ are needed to produce 3.40 g of NH$$_3$$? (Molar mass NH$$_3 = 17.03 g/$$mol)

Accepted Answer

$$3.40 	ext{ g} 	imes \frac{1 	ext{ mol}}{17.03 	ext{ g}} 	imes \frac{3 	ext{ mol H}_2}{2 	ext{ mol NH}_3} = 0.300 	ext{ mol}$$

Question 10

If 4.44 moles of H$$_2$$ and 3.44 moles of N$$_2$$ are reacted together according to $$3 	ext{H}_2 + 	ext{N}_2 ightarrow 2 	ext{NH}_3$$, what is the limiting reactant and how many moles of NH$$_3$$ can be produced?

Accepted Answer

H$$_2 is $$limiting; $$2.96$$ mol NH$$_3$$ produced

Question 11

Balance the following equation and identify the type of reaction: $$\_\_\_\_ 	ext{Fe} + \_\_\_\_ 	ext{O}_2 ightarrow \_\_\_\_ 	ext{Fe}_2	ext{O}_3$$

Accepted Answer

4 Fe + 3 O$$_2$$ → 2 Fe$$_2O$_3$$; Synthesis

Question 12

What is the molarity of a solution containing 32.5 g of NaCl dissolved in 500. mL of solution? (Molar mass NaCl = 58.44 g/mol)

Accepted Answer

$$\frac{32.5 	ext{ g}}{58.44 	ext{ g/mol}} = 0.556 	ext{ mol}; \frac{0.556 	ext{ mol}}{0.500 	ext{ L}} = 1.11 	ext{ M}$$

Question 13

How much of a 3.0 M HCl stock solution is needed to make 25 mL of 0.10 M HCl?

Accepted Answer

$$M_1V_1 = M_2V_2 ightarrow V_1$ = \frac{0.10 	imes 25}{3.0} = 0.83 mL$$

Question 14

Which of the following best describes the molecular geometry and hybridization of NH$$_3$$?

Accepted Answer

Trigonal pyramidal; sp$$^3$$

Question 15

What is the full electron configuration for Fe$$^{3+}$$?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$3d^5$$

Question 16

Write the net ionic equation for the reaction between sodium hydroxide and nitric acid.

Accepted Answer

$$	ext{OH}^- (aq) + 	ext{H}^+ (aq) ightarrow 	ext{H}_2	ext{O} (l)$$

Question 17

In the reaction of zinc with copper(II) sulfate, which substance is oxidized and which is reduced?

Accepted Answer

Zn is oxidized, Cu$$^{2+} is $$reduced

Question 18

A system emits 110 J of heat to the surroundings and has 65 J of work done on it. What is the change in internal energy ($$\Delta E$$)?

Accepted Answer

$$\Delta E = q + w = -110\ 	ext{J} + 65\ 	ext{J} = -45\ 	ext{J}$$

Question 19

Calculate the enthalpy change for the combustion of 1 mole of methane ($$	ext{CH}_4$$): $$	ext{CH}_4 + 2	ext{O}_2 ightarrow 	ext{CO}_2 + 2	ext{H}_2	ext{O} (g). $$Given: $$\Delta H_f^\circ(CO$_2) = -393.5 kJ/$$mol, $$\Delta H_f^\circ(H$_2O) = -285.8 kJ/$$mol, $$\Delta H_f^\circ(CH$_4) = -74.6 kJ/$$mol.

Accepted Answer

$$\Delta H = [-393.5 + 2(-285.8)] - [-74.6] = -890.5\ 	ext{kJ}$$

Question 20

What is the final temperature of 23.0 mL of water at 22.0$$^\circC $$when 860 J of heat is added? (Density = 1.00 g/mL, $$c = 4.18 J/g$^\circC)$$

Accepted Answer

$$q = mc\Delta T ightarrow \Delta T = \frac{860}{23.0 	imes 4.18} = 8.98^\circ	ext{C}; T_f = 22.0 + 8.98 = 30.98^\circ	ext{C}$$

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