Q: A sample of pitchblende contains 84.2 g and is made up of 71.4 g uranium and oxygen as the only other element. How many grams of uranium can be obtained from 102 g of pitchblende?

$$\frac{71.4}{84.2} \times 102 = 86.5 g$$

Q: A compound contains 77 g of xenon and 224 g of fluorine. What is the mass percent of xenon in the compound?

$$\frac{77}{77+224} \times 100 = 25.6\%$$

Question 1

Which of the following statements best describes the Law of Conservation of Mass?

Accepted Answer

The total mass of reactants and products in a chemical reaction remains constant.

Question 2

A sample of pitchblende contains 84.2 g and is made up of 71.4 g uranium and oxygen as the only other element. How many grams of uranium can be obtained from 102 g of pitchblende?

Accepted Answer

$$\frac{71.4}{84.2} 	imes 102 = 86.5 g$$

Question 3

Which experiment led to the discovery of the nucleus of the atom?

Accepted Answer

Rutherford's gold foil experiment

Question 4

Which of the following is NOT a postulate of Dalton's Atomic Theory?

Accepted Answer

Atoms can be created or destroyed in chemical reactions.

Question 5

A compound contains 77 g of xenon and 224 g of fluorine. What is the mass percent of xenon in the compound?

Accepted Answer

$$\frac{77}{77+224} 	imes 100 = 25.6\%$$

Question 6

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 7

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

Accepted Answer

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

Question 8

Which of the following elements has the highest first ionization energy?

Accepted Answer

He

Question 9

What is the electron configuration for a ground state oxygen atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^4$$

Question 10

Which statement about isotopes is correct?

Accepted Answer

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

Question 11

Which of the following best describes the relationship between wavelength ($$\lambda$$), frequency ($$
u$$), and speed of light ($$c$$)?

Accepted Answer

$$c = \lambda 
u$$

Question 12

Which orbital has the highest energy in the $$n=4$$ shell?

Accepted Answer

$$4f$$

Question 13

A 2.76 g sample of fluorite contains 1.42 g of calcium. What is the mass fraction of calcium in the sample?

Accepted Answer

$$\frac{1.42}{2.76} = 0.514$$

Question 14

Which of the following best describes a cation?

Accepted Answer

An atom that has lost one or more electrons and has a positive charge.

Question 15

Which principle states that electrons fill the lowest energy orbitals first?

Accepted Answer

Aufbau principle

Question 16

Which of the following elements is most likely to be chemically similar to sodium (Na)?

Accepted Answer

K

Question 17

Which quantum number specifies the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number ($$m_l)$$

Question 18

Which of the following is a correct statement about atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases from left to right across a period.

Question 19

Which of the following best describes the emission spectrum of hydrogen?

Accepted Answer

It consists of discrete lines corresponding to specific energy transitions of electrons.

Question 20

Which rule states that electrons occupy orbitals singly before pairing up?

Accepted Answer

Hund's rule

Atomic Structure and Laws of Chemical Combination: Study Notes for General Chemistry

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