Q: Which of the following best describes Avogadro's number?

The number of particles in one mole of a substance, $6.022 \times 10^{23}$.

Question 1

Which of the following statements best describes the difference between a compound and a mixture?

Accepted Answer

A compound is a substance composed of two or more elements chemically combined in fixed proportions, while a mixture consists of two or more substances physically combined in variable proportions.

Question 2

A student measures the mass of a sample three times and gets values that are very close to each other, but far from the true value. Which term best describes the student's measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

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

Accepted Answer

Melting of ice to form liquid water.

Question 4

Which of the following best describes the Lewis theory of bonding?

Accepted Answer

Atoms achieve stable electron configurations by sharing, gaining, or losing electrons to form bonds, often represented by dot structures.

Question 5

A sample of light has a frequency of $6.0 	imes 10^{14}\ \mathrm{Hz}$. What is its wavelength in nanometers? (Speed of light $c = 3.00 	imes 10^8\ \mathrm{m/s}$)

Accepted Answer

$500\ \mathrm{nm}$

Question 6

Which experiment provided evidence for the existence of the atomic nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 7

Which of the following is the correct balanced molecular equation for the neutralization reaction between hydrochloric acid and sodium hydroxide?

Accepted Answer

$\mathrm{HCl}(aq) + \mathrm{NaOH}(aq) \rightarrow \mathrm{NaCl}(aq) + \mathrm{H_2O}(l)$

Question 8

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 9

A 25.0 g sample of ethanol ($\mathrm{C_2H_5OH}$) is burned in excess oxygen. How many moles of carbon dioxide ($\mathrm{CO_2}$) are produced? (Molar mass of $\mathrm{C_2H_5OH} = 46.0\ \mathrm{g/mol}$; balanced equation: $\mathrm{C_2H_5OH} + 3\mathrm{O_2} \rightarrow 2\mathrm{CO_2} + 3\mathrm{H_2O}$)

Accepted Answer

$1.09\ \mathrm{mol}$

Question 10

Which of the following is a redox reaction?

Accepted Answer

$\mathrm{Zn}(s) + \mathrm{CuSO_4}(aq) \rightarrow \mathrm{ZnSO_4}(aq) + \mathrm{Cu}(s)$

Question 11

Which of the following best describes Avogadro's number?

Accepted Answer

The number of particles in one mole of a substance, $6.022 	imes 10^{23}$.

Question 12

A gas occupies a volume of $2.50\ \mathrm{L}$ at $1.00\ \mathrm{atm}$ and $300\ \mathrm{K}$. What will be its volume at $2.00\ \mathrm{atm}$ and $300\ \mathrm{K}$, assuming ideal gas behavior?

Accepted Answer

$1.25\ \mathrm{L}$

Question 13

Which of the following is the correct net ionic equation for the reaction between aqueous solutions of silver nitrate and sodium chloride?

Accepted Answer

$\mathrm{Ag^+}(aq) + \mathrm{Cl^-}(aq) \rightarrow \mathrm{AgCl}(s)$

Question 14

Which of the following statements about the law of conservation of energy is correct?

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another.

Question 15

A solution is prepared by dissolving $10.0\ \mathrm{g}$ of NaCl in enough water to make $500.0\ \mathrm{mL}$ of solution. What is the molarity of the solution? (Molar mass of NaCl = $58.44\ \mathrm{g/mol}$)

Accepted Answer

$0.342\ \mathrm{M}$

Question 16

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have delocalized electrons that can move freely throughout the structure.

Question 17

Which of the following is a correct statement about the periodic table?

Accepted Answer

Elements in the same group have similar chemical properties because they have the same number of valence electrons.

Question 18

A student is asked to identify whether a sample is a heterogeneous or homogeneous mixture. Which of the following is a correct example of a heterogeneous mixture?

Accepted Answer

Salad with lettuce, tomatoes, and cucumbers.

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