Q: A sample contains $$3.0$$ moles of sodium chloride ($$\mathrm{NaCl}). $$How many formula units are present? ($$1$$ mole $$= 6.022 \times 10$$^{23}$$ units)

$$1.81 \times 10$$^{24}$$ formula units

Q: Which of the following is the correct definition of density?

$$\text{Density} = \frac{\text{mass}}{\text{volume}}$$

Q: Which of the following is the correct formula for calculating percent composition by mass?

$$\text{Percent composition} = \frac{\text{mass of element}}{\text{total mass}} \times 100$$

Question 1

Which of the following correctly applies the significant figure rules when adding $$12.345$$ and $$7.1$$?

Accepted Answer

$$12.345 + 7.1 = 19.4 ($$rounded to the tenths place)

Question 2

Express $$0.00056 in $$scientific notation.

Accepted Answer

$$5.6 	imes 10$$^{-4}$$

Question 3

Which of the following is a physical change?

Accepted Answer

Melting ice

Question 4

Convert $$25^{\circ}$$\mathrm{C}$$ to Fahrenheit using the correct formula.

Accepted Answer

$$25^{\circ}$$\mathrm{C} = $$77^{\circ}$$\mathrm{F}$$

Question 5

Which of the following is a homogeneous mixture?

Accepted Answer

Air

Question 6

Which statement best describes a compound?

Accepted Answer

A substance made of two or more elements chemically bonded together

Question 7

A sample contains $$3.0$$ moles of sodium chloride ($$\mathrm{NaCl}). $$How many formula units are present? ($$1$$ mole $$= 6.022 	imes 10$$^{23}$$ units)

Accepted Answer

$$1.81 	imes 10$$^{24}$$ formula units

Question 8

Which of the following is the correct conversion from $$100$$ grams of water to moles? ($$\mathrm{H_2O}$$, molar mass $$= 18.0 g/$$mol)

Accepted Answer

$$100 \div 18.0 = 5.56$$ moles

Question 9

Which of the following is a chemical property?

Accepted Answer

Reactivity with acid

Question 10

A student mixes $$50 mL of$$ $$1.0 M$$ $$	ext{NaOH}$$ with $$50 mL of$$ $$1.0 M$$ $$	ext{HCl}. $$What is the final solution?

Accepted Answer

A neutral solution of $$	ext{NaCl}$$ and water

Question 11

Which of the following best describes the difference between a heterogeneous and homogeneous mixture?

Accepted Answer

Homogeneous mixtures have uniform composition; heterogeneous mixtures do not

Question 12

Which equation is used to convert Celsius to Kelvin?

Accepted Answer

$$K = ^{\circ}C + 273.15$$

Question 13

A chemical reaction produces $$2.5$$ moles of carbon dioxide ($$\mathrm{CO_2$}). $$What is the mass of $$\mathrm{CO_2$}$$ produced? (Molar mass $$= 44.0 g/$$mol)

Accepted Answer

$$2.5 	imes 44.0 = 110 g$$

Question 14

Which of the following is the correct definition of density?

Accepted Answer

$$	ext{Density} = \frac{	ext{mass}}{	ext{volume}}$$

Question 15

A solution contains $$10 g of $$salt in $$100 mL of $$water. What is the concentration in g/mL?

Accepted Answer

$$0.10 g/mL$$

Question 16

Which of the following is NOT a chemical change?

Accepted Answer

Evaporation of water

Question 17

A student needs to convert $$250 mL to $$liters. What is the correct conversion?

Accepted Answer

$$250 \div 1000 = 0.25 L$$

Question 18

Which of the following best describes an element?

Accepted Answer

A pure substance that cannot be broken down by chemical means

Question 19

Which of the following is the correct formula for calculating percent composition by mass?

Accepted Answer

$$	ext{Percent composition} = \frac{	ext{mass of element}}{	ext{total mass}} 	imes 100$$

Exam 1 Study Guide: Introduction to Chemistry (CHM 130, Chapters 1–3)

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