Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 5: Problem 17

According to the law of conservation of mass, mass cannot be gained or destroyed in a chemical reaction. Why can't you simply add the masses of two reactants to determine the total mass of product?

Short Answer

Expert verified
In a chemical reaction, atoms within reactant molecules rearrange themselves to form product molecules, so merely adding the masses of reactants will not give the exact mass of products. We must balance the chemical equation, use mole ratios, and consider the rearrangement of atoms to determine the total mass of products accurately. The law of conservation of mass holds true at an atomic level, meaning the number and type of atoms remain constant in a closed system throughout the reaction.

Step by step solution

01

: In a chemical reaction, atoms within reactant molecules rearrange themselves to form product molecules. The total mass of atoms remains conserved, but the individual masses of different types of molecules may change. Therefore, merely adding the masses of reactants will not give you the exact mass of products. #Step 2: Balancing the chemical equation#

: Before determining the mass of products, we need to balance the chemical equation to ensure the number of atoms in reactants and products is the same for each element. By following the law of conservation of mass, we can ensure that the correct amount of reactants is used, and the correct mass of products is formed. #Step 3: Using mole ratios to find the total mass of product#
02

: Once the chemical equation is balanced, we can use the mole ratio of reactants and products to determine the mass of each product formed. We establish these relationships by converting the masses of reactants into moles, using the molecular weights of each substance. For example, if the balanced equation is: \[A + 2B \to C + 3D\] Suppose the mass of 'A' and 'B' reactants are given. To determine the mass of products 'C' and 'D', you would: 1. Convert the mass of reactant 'A' to moles using its molecular weight 2. Convert the mass of reactant 'B' to moles using its molecular weight 3. Compare the mole ratios in the balanced equation and see which reactant is in excess or limiting 4. Determine the moles of products 'C' and 'D' according to the balanced equation 5. Convert the moles of product 'C' back into mass using its molecular weight 6. Convert the moles of product 'D' back into mass using its molecular weight 7. Sum the masses of 'C' and 'D' to find the total mass of products #Step 4: Recognizing that mass is conserved at an atomic level#

: In conclusion, the reason why we can't simply add the masses of reactants to determine the total mass of products is that a chemical reaction involves the rearrangement of atoms, not just the combination of masses. We must consider the balanced chemical equation and the corresponding mole ratios to accurately determine the total mass of product. The law of conservation of mass still holds true but at an atomic level, meaning the number and type of atoms remain constant in a closed system throughout the reaction.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Ammonia reacts with \(\mathrm{O}_{2}\) to form either \(\mathrm{NO}(g)\) or \(\mathrm{NO}_{2}(g)\) according to these unbalanced equations: $$\begin{array}{l}\mathrm{NH}_{3}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{NO}(g)+\mathrm{H}_{2} \mathrm{O}(g) \\\\\mathrm{NH}_{3}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{NO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)\end{array}$$ In a certain experiment 2.00 moles of \(\mathrm{NH}_{3}(g)\) and 10.00 moles of \(\mathbf{O}_{2}(g)\) are contained in a closed flask. After the reaction is complete, 6.75 moles of \(\mathbf{O}_{2}(g)\) remains. Calculate the number of moles of \(\mathrm{NO}(g)\) in the product mixture: (Hint: You cannot do this problem by adding the balanced equations because you cannot assume that the two reactions will occur with equal probability.)

Many cereals are made with high moisture content so that the cereal can be formed into various shapes before it is dried. A cereal product containing \(58 \% \mathrm{H}_{2} \mathrm{O}\) by mass is produced at the rate of \(1000 .\) kg/h. What mass of water must be evaporated per hour if the final product contains only \(20 . \%\) water?

Terephthalic acid is an important chemical used in the manufacture of polyesters and plasticizers. It contains only \(\mathrm{C}, \mathrm{H}\) and O. Combustion of \(19.81 \mathrm{mg}\) terephthalic acid produces \(41.98 \mathrm{mg} \mathrm{CO}_{2}\) and \(6.45 \mathrm{mg} \mathrm{H}_{2} \mathrm{O} .\) If 0.250 mole of terephthalic acid has a mass of \(41.5 \mathrm{g},\) determine the molecular formula for terephthalic acid.

Commercial brass, an alloy of Zn and Cu, reacts with hydrochloric acid as follows: $$\mathrm{Zn}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{ZnCl}_{2}(a q)+\mathrm{H}_{2}(g)$$ (Cu does not react with HCl.) When 0.5065 g of a certain brass alloy is reacted with excess \(\mathrm{HCl}, 0.0985 \mathrm{g}\) \(\mathrm{ZnCl}_{2}\) is eventually isolated. a. What is the composition of the brass by mass? b. How could this result be checked without changing the above procedure?

Arrange the following substances in order of increasing mass percent of carbon. a. caffeine, \(\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2}\) b. sucrose, \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\) c. ethanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\)
See all solutions

Recommended explanations on Chemistry Textbooks

Chemical Reactions

Read Explanation

Ionic and Molecular Compounds

Read Explanation

Physical Chemistry

Read Explanation

Chemistry Branches

Read Explanation

The Earths Atmosphere

Read Explanation

Kinetics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free