Q: Convert 2.50 pounds to kilograms. (1 pound = 453.59 grams)

$$2.50 \times \frac{453.59}{1000} = 1.13 kg$$

Question 1

Which of the following best describes the Law of Constant Composition?

Accepted Answer

A compound always contains the same elements in the same proportion by mass.

Question 2

Given two samples of carbon dioxide: Sample 1 contains 4.8 g O and 1.8 g C; Sample 2 contains 17.1 g O and 6.4 g C. Are these samples consistent with the Law of Constant Composition? Show your reasoning.

Accepted Answer

Yes, because the ratio $$\frac{4.8}{1.8} = 2.67$$ and $$\frac{17.1}{6.4} = 2.67$$, so the mass ratios are the same.

Question 3

Which of the following is the correct chemical formula for a compound containing two aluminum atoms for every three oxygen atoms?

Accepted Answer

$$\mathrm{Al_2O_3}$$

Question 4

A sample of natural gas (methane) reacts with 96 g of oxygen to produce 66 g of carbon dioxide. According to the Law of Conservation of Mass, how many grams of water are produced?

Accepted Answer

30 g

Question 5

Which of the following best describes an endothermic reaction?

Accepted Answer

A reaction that absorbs energy from its surroundings, resulting in products with higher potential energy than the reactants.

Question 6

Convert 2.50 pounds to kilograms. (1 pound = 453.59 grams)

Accepted Answer

$$2.50 	imes \frac{453.59}{1000} = 1.13 kg$$

Question 7

Which of the following is a physical change?

Accepted Answer

Sugar dissolves in hot water.

Question 8

A block has a mass of 25.0 g and a volume of 17.0 mL. What is its density?

Accepted Answer

$$\frac{25.0}{17.0} = 1.47 g/mL$$

Question 9

Which of the following substances is a homogeneous mixture?

Accepted Answer

Urine

Question 10

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes are atoms of the same element with different numbers of neutrons.

Question 11

Which group does chlorine belong to on the periodic table, and what is a typical property of this group?

Accepted Answer

Group 17 (halogens); they typically form $$-1$$ ions.

Question 12

Which of the following is the correct chemical notation for chlorine-35?

Accepted Answer

$$^{35}\mathrm{Cl}$$

Question 13

A neutral sodium atom has 11 protons. Which of the following is true?

Accepted Answer

It has 11 electrons.

Question 14

Which of the following best describes a cation?

Accepted Answer

A positively charged ion.

Question 15

Which of the following is a chemical property of iron?

Accepted Answer

Reacts with oxygen to form rust.

Question 16

Convert $$37.0\ ^\circ\mathrm{C} to $$Kelvin.

Accepted Answer

$$37.0 + 273.15 = 310.15\ \mathrm{K}$$

Question 17

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A mixture in which the composition is not uniform throughout.

Question 18

Which of the following is the correct formula for a compound containing three oxygen atoms for every sulfur atom?

Accepted Answer

$$\mathrm{SO_3$}$$

Question 19

Which of the following is a correct statement about the conservation of mass in a chemical reaction?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 20

Which of the following is a correct unit conversion for $$1.00\ \mathrm{m} to $$centimeters?

Accepted Answer

$$1.00 	imes 100 = 100\ \mathrm{cm}$$

Introduction to Chemistry: Compounds, Chemical Reactions, and Foundational Concepts

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