Q: Calculate the number of copper atoms in $$2.45$$ mol of copper. (Avogadro's number $$= 6.022 \times 10$$^{23}$$ atoms/mol)

$$1.48 \times 10$$^{24}$$ atoms

Q: Which of the following is the correct formula for calculating the average atomic mass of an element with two isotopes?

$$\text{Atomic mass} = (x_1$)(m_1$) + (x_2$)(m_2$)$$

Question 1

Which of the following best describes a chemical change?

Accepted Answer

Iron rusting in the presence of oxygen

Question 2

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

Accepted Answer

Law of Conservation of Mass

Question 3

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

Accepted Answer

Low accuracy and high precision

Question 4

Which of the following is NOT an SI base unit?

Accepted Answer

Gram

Question 5

A sample of water is decomposed into 16.0 g of oxygen and 2.0 g of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$8:1$$

Question 6

Which experiment provided the first measurement of the electron's charge?

Accepted Answer

Millikan's oil drop experiment

Question 7

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 8

A neutral atom of sodium ($$^{23}_{11}\mathrm{Na}) $$has how many electrons?

Accepted Answer

$$11$$

Question 9

Which of the following best explains why alkali metals are highly reactive?

Accepted Answer

They have one electron in their outermost shell, which is easily lost.

Question 10

Calculate the number of copper atoms in $$2.45$$ mol of copper. (Avogadro's number $$= 6.022 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$1.48 	imes 10$$^{24}$$ atoms

Question 11

Which of the following is a derived SI unit?

Accepted Answer

Newton

Question 12

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

Accepted Answer

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 13

Which of the following is the correct formula for calculating the average atomic mass of an element with two isotopes?

Accepted Answer

$$	ext{Atomic mass} = (x_1$)(m_1$) + (x_2$)(m_2$)$$

Question 14

A student needs to convert $$25.0$$ inches to centimeters. Given $$1$$ inch $$= 2.54 cm$$, what is the correct answer with the proper number of significant figures?

Accepted Answer

$$63.5 cm$$

Question 15

Which of the following statements about ions is true?

Accepted Answer

Cations have more protons than electrons.

Question 16

Which of the following is a physical property?

Accepted Answer

Melting point

Question 17

Which scientist is credited with the discovery of the nucleus through the gold foil experiment?

Accepted Answer

Ernest Rutherford

Question 18

Which of the following best describes the periodic law?

Accepted Answer

Properties of elements recur periodically when arranged by increasing atomic number.

Question 19

A sample contains $$3.00$$ mol of aluminum. What is the mass of this sample? (Molar mass of Al $$= 26.98 g/$$mol)

Accepted Answer

$$80.94 g$$

Question 20

Which of the following is a correct statement about noble gases?

Accepted Answer

They have a full outer electron shell and are very unreactive.

Measurement, Physical and Chemical Change, and Energy in Chemistry

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