Q: A sample contains $$2.0$$ moles of carbon atoms. How many atoms are present in the sample? (Avogadro's number $$= 6.022 \times 10$$^{23}$$ atoms/mol)

$$1.20 \times 10$$^{24}$$ atoms

Question 1

Which of the following best describes a chemical change, as opposed to a physical change, using a real-world example?

Accepted Answer

A piece of iron rusting when left outside.

Question 2

A student measures the mass of a sample as $$4.50 g$$, $$4.48 g$$, and $$4.51 g in $$three trials. The true mass is $$4.00 g. $$Which statement best describes the accuracy and precision of these measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Which of the following is the correct scientific notation for the number $$0.000345$$?

Accepted Answer

$$3.45 	imes 10$$^{-4}$$

Question 4

A sample of water is heated from $$25.0\ ^\circ\mathrm{C} to$$ $$75.0\ ^\circ\mathrm{C}. If $$the mass of the water is $$100.0 g $$and the specific heat capacity is $$4.18\ \mathrm{J}/\mathrm{g}\cdot\mathrm{C}$$, how much energy is absorbed?

Accepted Answer

$$20,900\ \mathrm{J}$$

Question 5

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 6

Which of the following is the correct electron configuration for a neutral atom of sodium ($$Z=11$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^1$$

Question 7

Which of the following best explains why metals tend to have high electrical conductivity?

Accepted Answer

Metals have delocalized electrons that can move freely throughout the structure.

Question 8

A chemist needs to convert $$5.00$$ kilometers to centimeters. Which of the following is the correct answer?

Accepted Answer

$$5.00 	imes 10^5$ cm

Question 9

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

Accepted Answer

Neon ($$\mathrm{Ne})$$

Question 10

Which of the following best describes the law of conservation of mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 11

Which of the following is a correct statement about the periodic trend in atomic size?

Accepted Answer

Atomic size increases down a group and decreases across a period from left to right.

Question 12

A sample contains $$2.0$$ moles of carbon atoms. How many atoms are present in the sample? (Avogadro's number $$= 6.022 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$1.20 	imes 10$$^{24}$$ atoms

Question 13

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A mixture in which the composition is not uniform throughout.

Question 14

Which of the following is the correct symbol for an ion with 17 protons and 18 electrons?

Accepted Answer

$$\mathrm{Cl}^-$$

Question 15

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

Accepted Answer

They have completely filled valence electron shells.

Question 16

A student is asked to round the number $$0.0045678 to $$three significant figures. What is the correct answer?

Accepted Answer

$$0.00457$$

Question 17

Which of the following best describes the quantum mechanical model of the atom?

Accepted Answer

Electrons occupy orbitals, which are regions of space where there is a high probability of finding an electron.

Question 18

Which of the following is the correct order of increasing metallic character among the elements: $$\mathrm{Na}$$, $$\mathrm{Mg}$$, $$\mathrm{Al}$$, $$\mathrm{Si}$$?

Accepted Answer

$$\mathrm{Si} \u003c \mathrm{Al} \u003c \mathrm{Mg} \u003c \mathrm{Na}$$

Question 19

A hospital uses a solution containing $$0.9\%$$ NaCl by mass. If a nurse needs to prepare $$500 g of $$this solution, how many grams of NaCl are required?

Accepted Answer

$$4.5 g$$

Question 20

Which of the following best describes the relationship between energy, frequency, and wavelength for electromagnetic radiation?

Accepted Answer

Energy increases as frequency increases and wavelength decreases.

Introduction to Chemistry: Exam 1 Study Guide

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