Q: Calculate the number of ethanol molecules in $$15.20\ \text{g} of $$ethanol ($$\mathrm{CH_3CH_2OH}). $$Molar mass = $$46.07\ \text{g/mol}. $$Use Avogadro’s number $$6.022 \times 10$$^{23}$$.

$$1.99 \times 10$$^{23}$$ molecules

Q: What is the net ionic equation for the reaction between FeCl$$_3 (aq) $$and Pb(NO$$_3$$)$$_2 (aq$$)?

$$3\text{Pb}^{2+} (aq) + 6\text{Cl}^- (aq) \rightarrow 3\text{PbCl}_2 (s)$$

Question 1

Which of the following best describes the result of Rutherford’s gold foil experiment regarding atomic structure?

Accepted Answer

Atoms have a dense, positively charged nucleus surrounded by electrons.

Question 2

A solution is prepared by dissolving 75.0 g of NaCl in 250.0 g of water. What is the mass percent of NaCl in the solution? Use the formula: $$	ext{Mass percent} = \frac{	ext{mass of solute}}{	ext{mass of solution}} 	imes 100\%$$

Accepted Answer

$$23.1\%$$

Question 3

Which of the following is a homogeneous mixture?

Accepted Answer

Salt water

Question 4

A 25 lb child requires $$0.005\ 	ext{g/kg} of a $$drug. (1 lb = 0.454 kg) How many grams of the drug does the child need?

Accepted Answer

$$0.057\ 	ext{g}$$

Question 5

Which of the following is an example of a physical change?

Accepted Answer

Melting of ice

Question 6

What is the molarity of a solution made by diluting $$50.0\ 	ext{mL} of a$$ $$5.5\ 	ext{M}$$ solution to a final volume of $$160.0\ 	ext{mL}$$? Use $$M_1V_1 = M_2V_2.$$

Accepted Answer

$$1.72\ 	ext{M}$$

Question 7

Which of the following elements is a halogen in period 2?

Accepted Answer

Fluorine

Question 8

Calculate the number of ethanol molecules in $$15.20\ 	ext{g} of $$ethanol ($$\mathrm{CH_3CH_2OH}). $$Molar mass = $$46.07\ 	ext{g/mol}. $$Use Avogadro’s number $$6.022 	imes 10$$^{23}$$.

Accepted Answer

$$1.99 	imes 10$$^{23}$$ molecules

Question 9

Which of the following compounds is a strong electrolyte?

Accepted Answer

NaCl (aq)

Question 10

What is the net ionic equation for the reaction between FeCl$$_3 (aq) $$and Pb(NO$$_3$$)$$_2 (aq$$)?

Accepted Answer

$$3	ext{Pb}^{2+} (aq) + 6	ext{Cl}^- (aq) ightarrow 3	ext{PbCl}_2 (s)$$

Question 11

A sample of gas initially occupies $$5.50\ 	ext{L} at a $$pressure of $$0.750\ 	ext{atm} at$$ $$13.0^\circ	ext{C}. $$What will the pressure be if the volume is changed to $$1.50\ 	ext{L} ($$temperature constant)? Use $$P_1V_1 = P_2V_2.$$

Accepted Answer

$$2.75\ 	ext{atm}$$

Question 12

Which of the following best describes what happens to a blood cell placed in a solution with a higher salt concentration than the cell?

Accepted Answer

The cell shrinks due to water leaving the cell (crenation).

Question 13

What is the pH of a solution with $$[	ext{H}_3	ext{O}^+] = 5.8 	imes 10$$^{-4}$$\ 	ext{M}$$? Use $$	ext{pH} = -\log_{10}[	ext{H}_3	ext{O}^+].$$

Accepted Answer

$$3.24$$

Question 14

Which of the following is a covalent compound?

Accepted Answer

CO$$_2$$

Question 15

Which element has 83 protons, 126 neutrons, and 80 electrons?

Accepted Answer

$$^{209}_{83}	ext{Bi}^{3+}$$

Question 16

Which of the following is an element that exists as a liquid and is diatomic at room temperature?

Accepted Answer

Bromine

Question 17

What is the molecular shape and approximate bond angle of SO$$_3$$?

Accepted Answer

Trigonal planar, $$120^\circ$$

Question 18

Which of the following substances would be most soluble in benzene ($$\mathrm{C_6H_6}$$)?

Accepted Answer

Hexane ($$\mathrm{C_6H_{14}})$$

Question 19

Which of the following is a representative element?

Accepted Answer

Sodium (Na)

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