Question 1

Which of the following numbers has exactly three significant figures?

Accepted Answer

$$0.0300$$

Question 2

A student measures the mass of a sample as $$12.34 g $$and its volume as $$4.5 mL. $$What is the density of the sample, reported with the correct number of significant figures?

Accepted Answer

$$2.7\ \mathrm{g/mL}$$

Question 3

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

Accepted Answer

Iron rusting in moist air

Question 4

Which statement best describes the difference between physical and chemical changes?

Accepted Answer

Physical changes do not alter the chemical composition of a substance, while chemical changes result in new substances with different properties.

Question 5

Which of the following best explains why atomic emission spectra are unique for each element?

Accepted Answer

Each element has a unique arrangement of electrons, resulting in specific energy level transitions that emit light at characteristic wavelengths.

Question 6

Which of the following trends is observed as you move from left to right across a period in the periodic table?

Accepted Answer

Atomic size decreases and electronegativity increases.

Question 7

How many valence electrons does an atom of sulfur (S) have?

Accepted Answer

6

Question 8

Which of the following electron configurations represents a noble gas?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 9

What is the correct formula for magnesium chloride?

Accepted Answer

$$\mathrm{$$MgCl_2$$}$$

Question 10

Which of the following molecules is polar due to its bent shape?

Accepted Answer

$$\mathrm{H_2O}$$

Question 11

A compound is formed between aluminum and oxygen. What is the correct formula for this compound?

Accepted Answer

$$\mathrm{Al_2O_3}$$

Question 12

Which of the following best describes why noble gases are generally unreactive?

Accepted Answer

They have filled valence electron shells, making them stable.

Question 13

What is the correct name for the compound $$\mathrm{N_2O_5}$$?

Accepted Answer

Dinitrogen pentoxide

Question 14

Which of the following statements about polyatomic ions is correct?

Accepted Answer

Polyatomic ions are charged entities composed of two or more atoms covalently bonded, acting as a single unit.

Question 15

Which of the following best describes the trend in ionization energy across a period from left to right?

Accepted Answer

Ionization energy increases due to increasing nuclear charge.

Question 16

A sample contains $$60 mg of a $$substance. How many grams is this equivalent to?

Accepted Answer

$$0.060\ \mathrm{g}$$

Question 17

Which of the following is the correct Lewis dot structure for a chlorine atom?

Accepted Answer

A Cl symbol surrounded by seven dots

Question 18

Which of the following best explains why water ($$\mathrm{H_2O}) is a $$polar molecule?

Accepted Answer

It has a bent shape and the dipoles do not cancel out.

Question 19

Which of the following is the correct electron configuration for a sodium ion ($$\mathrm{Na^+}$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 20

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity generally increases across a period and decreases down a group.

Introduction to Chemistry: Essential Concepts and Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard