Q: Which of the following conversions is set up correctly using dimensional analysis to convert $5.00\ \mathrm{g}$ of carbon to moles? (Molar mass of carbon $= 12.01\ \mathrm{g/mol}$)

$5.00\ \mathrm{g} \times \frac{1\ \mathrm{mol}}{12.01\ \mathrm{g}}$

Question 1

A sample of seawater is analyzed in a laboratory. Which of the following best describes seawater?

Accepted Answer

A mixture, because it contains various dissolved salts and water that can be separated physically.

Question 2

A mixture of sand and salt is best separated by which method, and why?

Accepted Answer

Filtration, because sand is insoluble in water and can be separated from dissolved salt.

Question 3

Which of the following is a chemical property?

Accepted Answer

Ability of iron to rust when exposed to air.

Question 4

A block of metal has a mass of $54.0\ \mathrm{g}$ and a volume of $20.0\ \mathrm{cm}^3$. What is its density?

Accepted Answer

$2.70\ \mathrm{g/cm}^3$

Question 5

Calculate the number of significant figures in the result of the following calculation: $3.45 	imes 0.0340$

Accepted Answer

2

Question 6

Convert $250.0\ \mathrm{mL}$ to liters using dimensional analysis.

Accepted Answer

$0.250\ \mathrm{L}$

Question 7

A compound contains $12.0\ \mathrm{g}$ of carbon and $32.0\ \mathrm{g}$ of oxygen. What is the percent composition of oxygen in the compound?

Accepted Answer

$72.7\%$

Question 8

An atom has 17 protons, 18 neutrons, and 18 electrons. Which of the following statements is correct?

Accepted Answer

It is a chloride ion with a $-1$ charge.

Question 9

Which of the following is an isotope of $^{14}\mathrm{C}$?

Accepted Answer

An atom with 6 protons and 7 neutrons.

Question 10

Which of the following elements is a metalloid?

Accepted Answer

Silicon ($\mathrm{Si}$)

Question 11

What is the most likely charge of an ion formed by an atom of magnesium ($\mathrm{Mg}$)?

Accepted Answer

$+2$

Question 12

A sample of element X is analyzed by mass spectrometry and found to contain $60\%$ $^{63}\mathrm{X}$ (mass $= 63.0\ \mathrm{u}$) and $40\%$ $^{65}\mathrm{X}$ (mass $= 65.0\ \mathrm{u}$). What is the average atomic mass of X?

Accepted Answer

$64.0\ \mathrm{u}$

Question 13

How many atoms are present in $0.250\ \mathrm{mol}$ of copper ($\mathrm{Cu}$)? ($N_A = 6.022 	imes 10^{23}\ \mathrm{mol}^{-1}$)

Accepted Answer

$1.51 	imes 10^{23}$ atoms

Question 14

A student mixes $50.0\ \mathrm{mL}$ of water (density $= 1.00\ \mathrm{g/mL}$) with $50.0\ \mathrm{mL}$ of ethanol (density $= 0.789\ \mathrm{g/mL}$). What is the total mass of the mixture?

Accepted Answer

$89.5\ \mathrm{g}$

Question 15

Which of the following changes is a physical change?

Accepted Answer

Dissolving sugar in water.

Question 16

A student needs to prepare $0.500\ \mathrm{mol}$ of sodium chloride ($\mathrm{NaCl}$). What mass of $\mathrm{NaCl}$ is required? (Molar mass $= 58.44\ \mathrm{g/mol}$)

Accepted Answer

$29.22\ \mathrm{g}$

Question 17

Which of the following best describes the Law of Definite Proportions?

Accepted Answer

A compound always contains the same elements in the same ratio by mass.

Question 18

A sample of an unknown element contains atoms with 20 protons, 20 neutrons, and 18 electrons. Which statement is correct?

Accepted Answer

It is a $+2$ cation of calcium, since it has lost 2 electrons.

Question 19

Which of the following conversions is set up correctly using dimensional analysis to convert $5.00\ \mathrm{g}$ of carbon to moles? (Molar mass of carbon $= 12.01\ \mathrm{g/mol}$)

Accepted Answer

$5.00\ \mathrm{g} 	imes \frac{1\ \mathrm{mol}}{12.01\ \mathrm{g}}$

Question 20

A student calculates the density of a liquid as $0.876\ \mathrm{g/mL}$ using a mass of $43.8\ \mathrm{g}$ and a volume of $50.0\ \mathrm{mL}$. How many significant figures should the answer have?

Accepted Answer

3

Fundamental Concepts in General Chemistry: Classification, Properties, and Quantitative Relationships

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