🏷️ LIMITED TIME OFFER: GET 20% OFF GRADE+ YEARLY SUBSCRIPTION →

HomeClass Notes1,200,000US530,000

CHEM 6A Lecture 9: CHEM W3 Lec 10/20/17

79 views3 pages

3 Jun 2018

School

Department

Chemistry and Biochemistry

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Chapter 3: Law of Conservation of Mass

● In a Chemical Reaction: the number of substances may change and their properties will

change but the total amount of matter remains constant

● Chemical equations must be balanced

● They must have the same number of atoms of the same kind of both sides

● Balancing coefficients

Meaning of Chemical Equations

● 4Al (s) + 3O2(g) → 2Al2O3 (s)

● This equation means:

○ 4 Al atoms + 3 O2 molecules give 2 units of Al2O3

● But it also means:

○ 4 moles of Al + 3 moles of O2 give 2 moles of Al2O3

Writing Chemical Equations

● To write a chemical reaction, you need to know:

1. All reactant and formulas

2. All products and formulas

3. States of reactants and products (g) for gas, (l) for liquid, (s) for solid, (aq) for aqueous

(water) solution

4. Catalysts involved? High temp required?

5. Balancing coefficients identifying the relative amounts of each compound

Balancing Chemical Equations

1. Convert words to formulas

2. Begin to balance atoms: pick compound with most number of atoms and balance

3. Adjust coefficients until all atoms are balanced, may have fractions

4. Make sure all coefficients are integers in the simplest ratio, verify each atom is

balanced

5. Specify state of matter for each compound

E.g. Sodium solid reacts with water to produce aqueous sodium hydroxide and hydrogen gas

● Na (s) + H2O (l) → NaOH (aq) + H2 (g)

○ 1 Na on each side

○ 1 O on each side

○ 2 H on left, 3 H on right

● Na (s) + H2O (l) → NaOH (aq) + (½) H2 (g)

● 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

Unlock document

This preview shows page 1 of the document.
Unlock all 3 pages and 3 million more documents.

Already have an account? Log in

karolpcelar and 38244 others unlocked

CHEM 6A Full Course Notes

CHEM 6A Full Course Notes

Document Summary

In a chemical reaction: the number of substances may change and their properties will change but the total amount of matter remains constant. They must have the same number of atoms of the same kind of both sides. 4 al atoms + 3 o2 molecules give 2 units of al2o3. 4 moles of al + 3 moles of o2 give 2 moles of al2o3. High temp required: balancing coefficients identifying the relative amounts of each compound. Sodium solid reacts with water to produce aqueous sodium hydroxide and hydrogen gas. Na (s) + h2o (l) naoh (aq) + h2 (g) 2 h on left, 3 h on right. Na (s) + h2o (l) naoh (aq) + ( ) h2 (g) 2na (s) + 2h2o (l) 2naoh (aq) + h2 (g) E,g, reaction of solid tin and chlorine gas results in a product with tin(iv) ions. Write a balanced equation and name the product (a solid).

Related textbook solutions

Chemistry: Structure and Properties

ISBN: 9780134293936

Basic Chemistry

ISBN: 9780134138046

Principles of Chemistry Molecular Approach

ISBN: 9780134112831

Chemistry: Structure and Properties

ISBN: 9780134293936

Principles of Chemistry Molecular Approach

3rd Edition, 2014

ISBN: 9780321971944

Chemistry: A Molecular Approach

ISBN: 9780321809247

Chemistry: A Molecular Approach

ISBN: 9780134874371

Principles of Chemistry: A Molecular Approach

ISBN: 9780134895741

Chemistry: The Central Science

14th Edition, 2017

ISBN: 9780134414232

Related Documents

CHEM 6A Chapter Notes - Chapter 3: Bromine, Lanthanide, Rare Earth Element

greencrocodile812

CHEM 6A Lecture Notes - Lecture 3: Molar Mass, Molecular Mass, Empirical Formula

periwinkleguinea-pig299

CHEM 6A Study Guide - Final Guide: Molar Mass, Empirical Formula, Molecular Mass

byzantiumfly635

Related Questions

Science Tutor: Chemistry Name: Mixtures, Solutions, &Compounds: Chemical Equations Date Chemical Equations If a chemical symbol can be thought of as a letter and a chemical formula as a word in the language of chemistry, then a chemical equation is a statement or sentence. A chemical equation is a shorthand way of describing a chemical reaction between two or more substances. A "+ sign means "combines with." An arrow points away from the reactants and toward the products (See page 10), and an arrow means "yields." 2Na + Cl2 â 2NaCl means sodium combines with chlorine to yield sodiumn chloride (salt) Look closely at the equation above. Notice the "2" in front of NaCI on the right and Na on the left. That 2, called a coefficient, is necessary to make this equation balance. Remember Antoine Lavoisier? (Page 15) Matter is neither created nor destroyed in a chemical reaction. The same number of each kind of atom must be on both sides of a chemical equation. Because chlorine only exists as a molecule consisting of two chlorine atoms, it requires two atoms of sodium to yield two molecules of salt (NaCI). This illustrates another important law stated clearly by the French chemist Joseph-Louis Proust in 1799. Chemical compounds always combine in certain specific fixed proportions. Wherever sodium and chlorine combine, two atoms of sodium will be necessary to react with one molecule of gaseous chlorine. 1 . For the equation 2Mg + O2â 2MgO + energy: A. List the reactant or reactants 2Hato B. List the product or products C. How many atoms of magnesium does it take to combine with one molecule of oxygen? D. How many molecules of magnesium oxide are produced in this reaction? 2. Hydrogen can combine with oxygen to produce water. We could write the equation like this: H2 + O2 â H2O. But this equation is unbalanced! Rewrite this equation with the correct coefficients so that an atom of oxygen doesn't disappear! (Be careful. If you add a coefficient to one side you may have to adjust the other. Count all the atoms.) 3. Now that you have the idea, balance the following equations: A, Pho, â PbO + 02 C. Ca + H2O â Ca(OH)2 + H2 How is following a recipe to mix up a batch of biscuits (or any other food item) similar to Proust's law for chemical reactions? 4. OMark Twain Media, Inc., Publishers 17

I need help doing my lab homework, I missed lab that day because, I was sick and it's due.

Chemical Reactions and Equations Learning objectives To observe physical and chemical properties associated with chemical changes To be able to give evidence for the occurrence of a chemical reaction To write a balanced chemical equation To identify areaction as a combination, decomposition, precipitation, single or double replacement, or combustion reaction ntroduction When a substance undergoes a physical change, it changes its appearance but not its composition. For example, when ice melts to form water, it undergoes a physical change from solid to liquid. In a chemical change, the composition of a substance is changed to give a new substance with different physical and chemical properties. For example, when silver tarnishes, the shiny silver (Ag) changes to a dull gray silver sulfide (AgaS). Not only has the chemical formula changed from Ag to Agus, but also the physical properties (shininess) of the substance have changed. Some examples of physical and chemical changes are listed in Table 1 below. Table 1. Comparison of Physical and Chemical Changes Examples of Physical changes Examples and Evidence of Chemical Changes Change in state (melting, freezing, evaporating Formation of a gas (bubbles) subliming) Formation of a solid (precipitate) Change in size Tearing Change in Color Heat is given off or absorbed A solid dissolving in a solvent In a chemical reaction, atoms in the reactants are rearranged to produce new combinations of atoms in the products. However, the total number of atoms of each element in the reactants is equal to the total number of atoms in the products. This is true according to the Law of Conservation of Mass, which states that the total mass remains constant during a chemical reaction. In other words, matter cannot be created or destroyed in a chemical reaction. In a chemical equation, the reactants are shown on the left and the products are on the right. An arrow in between indicates that a chemical reaction occurs. Finally, the physical state of each compound is designated in parentheses after the chemical formula. Solid, liquid, gas, and aqueous (dissolved in water) are shown as(s,(n,(g), and (aq), respectively.