Q: Calculate the percent composition of sulfur in $$H_2SO_3. ($$Atomic masses: H = 1.01, S = 32.07, O = 16.00)

$$\frac{32.07}{82.09} \times 100 = 39.1\%$$

Q: How many moles of $$H_2$$ are needed to make 3.40 grams of $$NH_3$$? (Molar mass $$NH_3 = 17.03$ g/mol, reaction: 3H_2$$ + $$N_2$$ \rightarrow 2NH_3$$)

$$3.40 \div 17.03 = 0.200$$ mol $$NH_3$$, $$0.200 \times \frac{3}{2} = 0.300$$ mol $$H_2$$

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

$$M_1V_1 = M_2V_2$$, $$V_1$$ = \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 answer is correct?

Accepted Answer

$$4.89 	imes 10$$^{-3}$$ 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 5090000?

Accepted Answer

$$5.09 	imes 10$$^{6}$$

Question 5

A neutral atom of lithium (Li) has an atomic number of 3 and a mass number of 7. How many neutrons does it have?

Accepted Answer

4

Question 6

What is the correct name for the compound Mg3P2?

Accepted Answer

Magnesium phosphide

Question 7

Calculate the percent composition of sulfur in $$H_2SO_3. ($$Atomic masses: H = 1.01, S = 32.07, O = 16.00)

Accepted Answer

$$\frac{32.07}{82.09} 	imes 100 = 39.1\%$$

Question 8

How many grams of sulfur are in 4.58 g of $$H_2SO_3$$? (Use your answer from the previous question: 39.1% S)

Accepted Answer

$$4.58 	imes 0.391 = 1.79 g$$

Question 9

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

Accepted Answer

$$NO_2$$

Question 10

If the molar mass of lithium oxalate is 101.88 g/mol and its percent composition is 13.62% Li, 23.58% C, and 62.81% O, what is its molecular formula?

Accepted Answer

$$Li_2C_2O_4$$

Question 11

How many moles of $$H_2$$ are needed to make 3.40 grams of $$NH_3$$? (Molar mass $$NH_3 = 17.03$ g/mol, reaction: 3H_2$$ + $$N_2$$ \rightarrow 2NH_3$$)

Accepted Answer

$$3.40 \div 17.03 = 0.200$$ mol $$NH_3$$, $$0.200 	imes \frac{3}{2} = 0.300$$ mol $$H_2$$

Question 12

Balance the following equation and identify the reaction type: $$Fe + O_2$ \rightarrow Fe_2O_3$$

Accepted Answer

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

Question 13

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

$$\frac{32.5}{58.44} = 0.556$$ mol; $$\frac{0.556}{0.500} = 1.11 M$$

Question 14

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

Accepted Answer

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

Question 15

Draw the Lewis structure for $$NH_3. $$What is the molecular geometry and hybridization of the central atom?

Accepted Answer

Trigonal pyramidal, sp$$^3$$

Question 16

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

Accepted Answer

$$[Ar] 3d^5$

Question 17

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

Accepted Answer

$$OH^- + H^+ \rightarrow H_2O$$

Question 18

In the reaction $$Zn + $$CuSO_4$$ \rightarrow $$ZnSO_4$$ + Cu$$, which element is oxidized?

Accepted Answer

Zinc

Question 19

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

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

Question 20

Calculate the enthalpy change for the combustion of 1 mole of methane ($$CH_4). ($$Heat of formation: $$CO_2 = -393.5$ kJ/mol, H_2O$ (g) = -285.8$ kJ/mol, CH_4$ = -74.6 kJ/$$mol)

Accepted Answer

$$\Delta H = [(-393.5) + 2(-285.8)] - [(-74.6) + 2(0)] = -890.1 kJ$$

Question 21

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

Accepted Answer

$$\Delta T = \frac{q}{mc} = \frac{860}{23 	imes 4.18} = 8.98^\circC$$; $$T_f = 22.0 + 8.98 = 30.98^\circC$$

CHE 1101 Final Exam Review – Step-by-Step Chemistry Guidance

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