3.7 chem. eqs 3.8 balancing chem. eqs - department of...
Post on 18-Mar-2018
214 Views
Preview:
TRANSCRIPT
3.7 Chem. Eqs&
3.8 Balancing Chem. Eqs
Copyright © Houghton Mifflin Company. All rights reserved. 3–2
Chemical Equations
A chemical equation gives the chemical formulas of the reactants on the left of the arrow and the products on the right.
Reactants Product
C(s)
O2 (g)CO2 (g)
Copyright © Houghton Mifflin Company. All rights reserved. 3–3
Symbols Used in Equations
Symbols used in chemicalequations show
• the states of the reactants.
• the states of the products.
• the reaction conditions.
TABLE
Copyright © Houghton Mifflin Company. All rights reserved. 3–4
Chemical Equations are Balanced
In a balancedchemical reaction• atoms are not
gained or lost.
• the number of reactant atoms is equal to the number of product atoms.
Copyright © Houghton Mifflin Company. All rights reserved. 3–5
A Balanced Chemical Equation
In a balanced chemical equation,• there must be the same number of each type of atom on
the reactant side and on the product side of a balanced equation.
• numbers called coefficients are used in front of one or more formulas.
Al + S Al2S3 Not Balanced2Al + 3S Al2S3 Balanced
2 Al = 2 Al3 S = 3 S
Copyright © Houghton Mifflin Company. All rights reserved. 3–6
Learning Check
State the number of atoms of each element on thereactant side and the product side for each of thefollowing balanced equations.
A. P4(s) + 6Br2(l) 4 PBr3(g)
B. 2Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s)
Copyright © Houghton Mifflin Company. All rights reserved. 3–7
Solution
A. P4(s) + 6Br2(l) 4 PBr3(g)4 P 4 P12 Br 12 Br
B. 2Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s)2 Al 2 Al2 Fe 2 Fe3 O 3 O
Copyright © Houghton Mifflin Company. All rights reserved. 3–8
Learning Check
Determine if each equation is balanced or not.
A. Na(s) + N2(g) Na3N(s)
B. C2H4(g) + H2O(l) C2H5OH(l)
Copyright © Houghton Mifflin Company. All rights reserved. 3–9
Solution
Determine if each equation is balanced or not.
A. Na(s) + N2(g) Na3N(s)No. 2 N on reactant side, 1 N on product side.
1 Na on reactant side, 3 Na on product side.
B. C2H4(g) + H2O(l) C2H5OH(l)Yes. 2 C = 2 C
6 H = 6 H1 O = 1 O
Copyright © Houghton Mifflin Company. All rights reserved. 3–10
Guide to Balancing a Chemical Equation
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Copyright © Houghton Mifflin Company. All rights reserved. 3–11
To balance the following equation, Fe3O4(s) + H2(g) Fe(s) + H2O(l)
• work on one element at a time.• use only coefficients in front of formulas.• do not change any subscripts.Fe: Fe3O4(s) + H2(g) 3Fe(s) + H2O(l)
O: Fe3O4(s) + H2(g) 3Fe(s) + 4H2O(l)
H: Fe3O4(s) + 4H2(g) 3Fe(s) + 4H2O(l)
Steps in Balancing an Equation
Copyright © Houghton Mifflin Company. All rights reserved. 3–12
1. Write the equation with the correct formulas.NH3(g) + O2(g) NO(g) + H2O(g)
2. Determine if the equation is balanced.No, not all atoms are balanced.
3. Balance with coefficients in front of formulas. 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)
4. Check that atoms of each element are equal in reactants and products.
4 N (4 x 1 N) = 4 N (4 x 1 N)12 H (4 x 3 H) = 12 H (6 x 2 H)10 O (5 x 2 O) = 10 O (4 O + 6 O)
Balancing Chemical Equations
Copyright © Houghton Mifflin Company. All rights reserved. 3–13
Equation for A Chemical Reaction
Copyright © Houghton Mifflin Company. All rights reserved. 3–14
Checking a Balanced Equation
Reactants Products1 C atom = 1 C atom4 H atoms = 4 H atoms4 O atoms = 4 O atoms
Copyright © Houghton Mifflin Company. All rights reserved. 3–15
Check the balance of atoms in the following.
Fe3O4(s) + 4H2(g) 3Fe(s) + 4H2O(l)
A. Number of H atoms in products.
1) 2 2) 4 3) 8
B. Number of O atoms in reactants.
1) 2 2) 4 3) 8
C. Number of Fe atoms in reactants.
1) 1 2) 3 3) 4
Learning Check
Copyright © Houghton Mifflin Company. All rights reserved. 3–16
Fe3O4(s) + 4H2(g) 3Fe(s) + 4H2O(l)
A. Number of H atoms in products.3) 8 (4H2O)
B. Number of O atoms in reactants.2) 4 (Fe3O4)
C. Number of Fe atoms in reactants.2) 3 (Fe3O4)
Solution
Copyright © Houghton Mifflin Company. All rights reserved. 3–17
Balance each equation and list the coefficients in the balanced equation going from reactants to products:
A. __Mg(s) + __N2(g) __Mg3N2(s)
1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1
B. __Al(s) + __Cl2(g) __AlCl3(s)
1) 3, 3, 2 2) 1, 3, 1 3) 2, 3, 2
Learning Check
Copyright © Houghton Mifflin Company. All rights reserved. 3–18
A. 3) 3, 1, 13Mg(s) + 1N2(g) 1Mg3N2(s)
B. 3) 2, 3, 2
2Al(s) + 3Cl2(g) 2AlCl3(s)
Solution
Copyright © Houghton Mifflin Company. All rights reserved. 3–19
Equations with Polyatomic Ions
Copyright © Houghton Mifflin Company. All rights reserved. 3–20
Balancing with Polyatomic IonsMgCl2(aq) + Na3PO4(aq) NaCl(aq) + Mg3(PO4)2(s)
Balance PO43- as a unit
MgCl2(aq) + 2Na3PO4(aq) NaCl(aq) + Mg3(PO4)2(s)2 PO4
3- = 2 PO43-
Balance Mg and Cl3MgCl2(aq) + 2Na3PO4(aq) 6NaCl(aq) + Mg3(PO4)2(s)
3 Mg2+ = 3 Mg2+
6 Na+ = 6 Na+
6 Cl- = 6 Cl-
Copyright © Houghton Mifflin Company. All rights reserved. 3–21
Balance and list the coefficients from reactants to products.
A. __Fe2O3(s) + __C(s) __Fe(s) + __CO2(g)
1) 2, 3, 2, 3 2) 2, 3, 4, 3 3) 1, 1, 2, 3
B. __Al(s) + __FeO(s) __Fe(s) + __Al2O3(s)
1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1
C. __Al(s) + __H2SO4(aq) __Al2(SO4)3(aq) + __H2(g)
1) 3, 2, 1, 2 2) 2, 3, 1, 3 3) 2, 3, 2, 3
Learning Check
Copyright © Houghton Mifflin Company. All rights reserved. 3–22
A. 2) 2, 3, 4, 3 2Fe2O3(s) + 3C(s) 4Fe(s) + 3CO2(g)
B. 1) 2, 3, 3, 1 2Al(s) + 3FeO(s) 3Fe(s) + 1Al2O3(s)
C. 2) 2, 3, 1, 3 2Al(s) + 3H2SO4(aq) 1Al2(SO4)3(aq) + 3H2(g)
Solution
top related