Q: Chlorine has two main isotopes: $$\$$displaystyle ^{35}$$\mathrm{Cl} ($$mass = 34.97 amu, 75.77%) and $$\$$displaystyle ^{37}$$\mathrm{Cl} ($$mass = 36.97 amu, 24.23%). What is the average atomic mass of chlorine?

$$\displaystyle (0.7577 \times 34.97) + (0.2423 \times 36.97) = 35.45\ \mathrm{amu}$$

Question 1

Which of the following statements correctly describes the three subatomic particles in an atom?

Accepted Answer

Protons and neutrons have nearly the same mass, while electrons are much lighter.

Question 2

Which of the following is an example of isotopes?

Accepted Answer

Carbon-12 and Carbon-14, because they have the same number of protons but different numbers of neutrons.

Question 3

Given an atom with 17 protons, 18 neutrons, and 18 electrons, which is the correct atomic symbol?

Accepted Answer

$$\displaystyle \ ^{35}_{17}\mathrm{Cl}^{-}$$

Question 4

Which statement best defines the atomic mass unit (amu)?

Accepted Answer

It is defined as one twelfth the mass of a carbon-12 atom.

Question 5

Chlorine has two main isotopes: $$\$$displaystyle ^{35}$$\mathrm{Cl} ($$mass = 34.97 amu, 75.77%) and $$\$$displaystyle ^{37}$$\mathrm{Cl} ($$mass = 36.97 amu, 24.23%). What is the average atomic mass of chlorine?

Accepted Answer

$$\displaystyle (0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45\ \mathrm{amu}$$

Question 6

Which of the following is the empirical formula for glucose, whose molecular formula is $$\displaystyle \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$?

Accepted Answer

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

Question 7

Which statement best describes the periodic law?

Accepted Answer

The properties of elements are periodic functions of their atomic numbers.

Question 8

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

Accepted Answer

Iron rusting when exposed to air.

Question 9

Which of the following is an intensive property?

Accepted Answer

Density

Question 10

A student measures the mass of a sample as 12.345 g and the volume as 6.7 mL. What is the density, reported with the correct number of significant figures?

Accepted Answer

$$\displaystyle 1.8\ \mathrm{g/mL}$$

Question 11

Convert 25.0 $$\displaystyle ^\circ\mathrm{C} to $$Kelvin.

Accepted Answer

$$\displaystyle 298.2\ \mathrm{K}$$

Question 12

How many atoms are in 2.00 grams of magnesium ($$\displaystyle \mathrm{Mg}$$, molar mass = 24.31 g/mol)?

Accepted Answer

$$\displaystyle \frac{2.00}{24.31} 	imes 6.022 	imes 10$$^{23}$$ = 4.96 	imes 10$$^{22}$$ atoms

Question 13

Which of the following correctly relates the speed of light ($$\displaystyle c$$), wavelength ($$\displaystyle \lambda$$), and frequency ($$\displaystyle 
u) of $$electromagnetic radiation?

Accepted Answer

$$\displaystyle c = \lambda 
u$$

Question 14

A photon has a frequency of $$\displaystyle 6.0 	imes 10$$^{14}$$\ \mathrm{Hz}. $$What is its energy? ($$\displaystyle h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s})$$

Accepted Answer

$$\displaystyle E = h 
u = 6.626 	imes 10$$^{-34}$$ 	imes 6.0 	imes 10$$^{14}$$ = 4.0 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 15

According to the Bohr model, what happens when an electron in a hydrogen atom transitions from $$n=4 to$$ $$n=2$$?

Accepted Answer

A photon is emitted with energy equal to the difference between the two energy levels.

Question 16

Which set of quantum numbers is not allowed for an electron in an atom?

Accepted Answer

$$\displaystyle n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 17

Which of the following elements is a metalloid?

Accepted Answer

Silicon ($$\displaystyle \mathrm{Si})$$

Question 18

Which type of bond is formed between magnesium and oxygen in magnesium oxide ($$\displaystyle \mathrm{MgO}$$)?

Accepted Answer

Ionic bond

General Chemistry I: Unit 1 Core Concepts and Learning Outcomes

Guida di studio - Domande di pratica

Study guide - Flashcard