Chapter 07

12/11/23, 11:56 PM Chapter 07 Assignment https://session.masteringchemistry.com/myct/assignmentPrintView?assignmentID=11885466 1/22 Chapter 07 Assignment Due: 12:00am on Tuesday, December 12, 2023 You will receive no credit for items you complete after the assignment is due. Grading Policy Chapter 7 Reading Question 1 Part A Which of the following is a balanced equation for the reaction of aluminum, Al , and hydrochloric acid, HCl, to form aluminum chloride, AlCl 3 , and hydrogen, H 2 ? Hint 1. How to identify a balanced chemical equation. A balanced chemical equation is one in which the same number and types of atoms exist on both sides of an equation. Begin by counting the number of atoms of each element on one side, and confirm that the other side of the equation has the same number of atoms. See Section 7.1. ANSWER: Correct Core Chemistry Skill: Balancing a Chemical Equation A chemical equation is used to describe a chemical reaction. The reactants are written on the left, and the products are written on the right. A reaction arrow; which often is a symbol such as , is used to indicate the chemical change. The reactants and products are written using element symbols and chemical formulas with coefficients to indicate the quantity of each, either as moles or atoms. Terms such as heat may be written over the reaction arrow to indicate the condition applied on the reactants. Some features of chemical equations are described in the table Symbols Meaning (s), (l), (g), (aq) Physical state of the species (called phases ) + Separation of two or more species Separation of reactants and products or heat Reaction is heated A chemical equation should always be balanced, that is, the reactants must have the same number and type of atoms of each element as the products. To balance the chemical equation, the law of conservation of mass must be upheld, which means matter is neither created nor destroyed during a chemical reaction. How to balance a chemical equation The process of balancing chemical reactions can often feel like a trial and error process. When balancing a chemical equation, follow these general steps: 1. Start with the unbalanced equation, and write each reactant and product using the correct element symbols and chemical formulas. Keep in mind that each subscript indicates the number of atoms in the chemical formula in the unbalanced chemical reaction, and also in the final balanced chemical equation. 2. Add coefficients before each species to balance the number of atoms of each element on each side of the reaction arrow. This involves multiplying the added coefficient by the subscript in the chemical formula. Usually one element is adjusted with its coefficient to balance that element, and then the next element is often balanced with its coefficient, and the process continues until the chemical equation is balanced. 2 Al + 6 HCl 2 AlCl 3 + 3 H 2 Al + 6 HCl 2 AlCl 3 + 3 H 2 Al + 3 HCl AlCl 3 + H 2 Al + 6 HCl AlCl 3 + 3 H 2

12/11/23, 11:56 PM Chapter 07 Assignment https://session.masteringchemistry.com/myct/assignmentPrintView?assignmentID=11885466 2/22 3. Check the final chemical equation to ensure that it is balanced, keeping in mind that you might need to go back and forth between the elements to adjust the coefficients to produce a final, balanced chemical equation. 4. After checking the final chemical equation and verifying that all atoms are balanced, reduce the coefficients to the smallest whole-number ratio. Fractional coefficients are not the best form for a balanced chemical equation. Balancing example When balancing a chemical equation, keep in mind that the number of atoms of each element increases as the coefficient increases, such that the coefficients for several species may be affected by the adjustment of a single number. Take the example of the formation of water: There are four hydrogen atoms on the reactant side, , and four hydrogen atoms on the product side, . Now, change the coefficient before water to 4: : (not balanced) Notice that now there are eight hydrogen atoms and four oxygen atoms on the product side, but there are still only four hydrogen atoms and two oxygen atoms on the reactant side. The coefficients before both hydrogen gas, , and oxygen gas, , must now be adjusted to balance the equation: A properly balanced equation has all the coefficients in the smallest whole-number ratio; however, this equation does show the relationship between four moles of hydrogen gas and two moles of oxygen gas to form four moles of the product, water. Part A Balance the chemical equation by indicating the number of each species in the appropriate blanks. For this exercise, indicate coefficients of 1 explicitly. Match the numbers in the left column to the appropriate blanks in the chemical equations on the right. Make certain the chemical equation is complete before submitting your answer. Hint 1. How to approach the problem The following steps can be used to balance the equation: 1. Count each atom of each element on the reactant side and the product side. It may help to set up a table to compare the totals for the reactants and the products. 2. Add appropriate coefficients to balance the number of atoms of each element that appear in only one compound or formula on each side of the equation first. 3. Continue to add coefficients to balance remaining elements until the number of atoms of each element on both sides of the equation are balanced. 4. Make sure the coefficients are reduced to their lowest whole-number values. Hint 2. Determine the number of atoms of each element in the reactants and products How many atoms of each element are in the reactants and products of the unbalanced equation? _____ + _____ _____ + _____ Drag the appropriate labels to their respective targets. ANSWER: ANSWER: Help Reset 1 2 3 4 5 1 3 2 2 1 4

12/11/23, 11:56 PM Chapter 07 Assignment https://session.masteringchemistry.com/myct/assignmentPrintView?assignmentID=11885466 3/22 Correct In any balanced chemical equation, if the coefficient of any reactant or product is one, then it is not required to write the numeral 1, and the coefficient can be omitted. Hence, the equation is written as . Types of chemical reactions Using some general pattern, we can classify chemical reactions as: Combination reaction: Decomposition reaction: Single replacement reaction: Double replacement reaction: Combustion reaction in which carbon-containing compounds such as methane, ethane, and so on, burn in oxygen to produce carbon dioxide, water, and heat energy. Uniquely, the combustion reaction is one of the simplest reactions to balance. The carbon atoms are always balanced first, followed by the hydrogen atoms, and finally the oxygen atoms. Sometimes, fractional coefficients, such as 1/2, 3/2, 5/2, and so on, result, but all coefficients can be multiplied by two to obtain whole- number coefficients. Part B Listed are examples of several types of chemical equations. Each is only partially balanced. Complete the task of balancing each chemical equation. Drag the appropriate labels to their respective targets. Hint 1. How to approach the problem The following steps can be used to balance the equation: 1. Count each atom of each element on the reactant side and the product side. It may help to set up a table to compare the totals for the reactants and the products. 2. Add appropriate coefficients to balance the number of atoms of each element that appear in only one compound or formula on each side of the equation first. In these equations, some coefficients are already present. It may help to start with the elements present in the compound already balanced. 3. Continue to add coefficients to balance remaining elements until the number of atoms of each element on both sides of the equation are balanced. 4. When balancing equations with polyatomic ions, it may help to treat polyatomic ions as a single unit. For example, in is a polyatomic ion called the sulfate ion and is present on both reactant and product sides; thus, it can be treated as single unit while balancing. 5. Make sure the coefficients are reduced to their lowest whole-number values. Hint 2. Determine the number of atoms of each element for the combustion reaction Some of the species in these partially balanced chemical equations are already balanced using coefficients. When determining how many atoms of each element are on the product and the reactant sides, make sure to consider the coefficients already present. How many atoms of each element are indicated by the partially balanced chemical equation for the following combustion reaction? Drag the appropriate labels to their respective targets. ANSWER: Reset Help 1 2 3 4 5 3 (s) + 4 (l) 1 (s) + 4 (g)

12/11/23, 11:56 PM Chapter 07 Assignment https://session.masteringchemistry.com/myct/assignmentPrintView?assignmentID=11885466 4/22 ANSWER: Correct Part C When aluminum, , metal is dipped in an aqueous solution of hydrochloric acid, , hydrogen gas, , is produced with the formation of an aluminum chloride, , solution. Write the balanced chemical equation showing the phases of reactants and products. Express your answer as a chemical equation including phases. Hint 1. Write the unbalanced chemical equation Aluminum ( ), a group 3A (13) metal with a valency 3, reacts with aqueous solution of hydrochloric acid, , to give hydrogen, , gas and an aqueous solution of aluminum chloride, . In this reaction, aluminum displaces hydrogen in to form aluminum chloride, which is a salt. Write the unbalanced chemical equation using the correct formulas for each reactant and product. Help Reset Help Reset 1 3 4 5 6 2 2 6 2 2 3 5 1 3 4 3 3 3 2 2 2 2 2 2 2

12/11/23, 11:56 PM Chapter 07 Assignment https://session.masteringchemistry.com/myct/assignmentPrintView?assignmentID=11885466 5/22 Express your answer as chemical equation including phases. ANSWER: Hint 2. Determine the number of atoms of each element in the unbalanced equation The unbalanced chemical equation is . Drag the appropriate labels to their respective targets. ANSWER: ANSWER: Correct Since all of the elements have an equal number of atoms on the reactant and product sides, the equation is balanced. A chemical equation must be balanced with respect to mass because matter can be neither created nor destroyed. The equation must also be balanced with respect to charge because the total number of electrons does not change; this is called charge balance. Signs of a Chemical Reaction A chemical reaction is a process by which one or more substances transform into different substances via a chemical change. Sometimes, chemical reactions exhibit evidence that can be easily observed when they occur. Part A Which changes are evidence of a chemical reaction? Drag each item to the appropriate bin. Hint 1. Physical changes and chemical changes In a physical change , matter does not change its composition, although the appearance of the matter changes. For example, a physical change occurs when liquid water freezes, producing ice. The water does not change its composition: Liquid water and solid water (ice) are both composed of water molecules. Help Reset 2 3 4 1 1 1 2 1 1 3