Q: A sample contains 3.0 moles of oxygen atoms. How many atoms are present in the sample? (Avogadro's number $$ = 6.022 \times 10$$^{23}$$ )$$

$$ 1.81 \times 10$$^{24}$$ $$ atoms

Question 1

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

Accepted Answer

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

Question 2

Which of the following is an example of a heterogeneous mixture?

Accepted Answer

Sand and iron filings

Question 3

A student measures the mass of a sample three times and gets values close to each other but far from the true value. This demonstrates:

Accepted Answer

Low accuracy and high precision

Question 4

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

Accepted Answer

Melting of ice

Question 5

Which law states that in a chemical reaction, matter is neither created nor destroyed?

Accepted Answer

Law of conservation of mass

Question 6

Which of the following is the correct empirical formula for glucose ($$ \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 $$)?

Accepted Answer

$$ \mathrm{CH}_2\mathrm{O} $$

Question 7

Which of the following best describes an extensive property?

Accepted Answer

A property that depends on the amount of substance present, such as mass or volume.

Question 8

Which of the following is the correct scientific notation for 0.00056?

Accepted Answer

$$ 5.6 	imes 10$$^{-4}$$ $$

Question 9

A sample contains 3.0 moles of oxygen atoms. How many atoms are present in the sample? (Avogadro's number $$ = 6.022 	imes 10$$^{23}$$ )$$

Accepted Answer

$$ 1.81 	imes 10$$^{24}$$ $$ atoms

Question 10

Which of the following is NOT a correct match of element name and symbol?

Accepted Answer

Sodium - S

Question 11

Which statement best describes the difference between a scientific theory and a scientific law?

Accepted Answer

A scientific theory is a well-substantiated explanation, while a law is a statement that describes a consistent relationship observed in nature.

Question 12

Which of the following is a correct statement about covalent and ionic bonding?

Accepted Answer

Covalent bonding involves sharing electrons between atoms, while ionic bonding involves the transfer of electrons from one atom to another.

Question 13

Which of the following is the correct molecular formula for water?

Accepted Answer

$$ \mathrm{H}_2\mathrm{O} $$

Question 14

A chemical reaction occurs in which 8.0 g of hydrogen reacts with 64.0 g of oxygen to form water. According to the law of conservation of mass, what is the total mass of water produced?

Accepted Answer

72.0 g

Question 15

Which of the following is an example of deductive reasoning in chemistry?

Accepted Answer

Starting with the general law of conservation of mass and concluding that mass will be conserved in a specific chemical reaction.

Question 16

Which of the following best describes the difference between mass number and atomic number?

Accepted Answer

Mass number is the sum of protons and neutrons, while atomic number is the number of protons.

Question 17

Which of the following compounds is named correctly according to IUPAC rules?

Accepted Answer

NaCl - Sodium chloride

Question 18

Which of the following is a correct statement about significant figures?

Accepted Answer

Zeros between nonzero digits are always significant.

Question 19

A sample of ethanol has a mass of 46.0 g and a volume of 58.0 mL. What is its density?

Accepted Answer

$$ 0.793 \ \mathrm{g/mL} $$

Question 20

Which of the following is the correct conversion from Celsius to Kelvin for a temperature of $$25^\circ \mathrm{C}$$?

Accepted Answer

$$ 298 \ \mathrm{K} $$

General Chemistry Fundamentals: Key Concepts, Laws, and Compound Naming

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