11 Grade Chemistry Student Exploration: Chemical Equations

26 Jul 11 Grade Chemistry Student Exploration: Chemical Equations

To submit this assignment, save this document using your last name first initial followed by lesson name. Use the lesson name given in the assignment. For example “BalanceEquationsLab.docx” for Marie Poston should be “PostonM_BalanceEquationsLab.docx”. Click in the       and type to enter your answers.

Gizmo Warm-up

Burning is an example of a chemical reaction. The law of conservation of matter states that no atoms are created or destroyed in a chemical reaction. Therefore, a balanced chemical equation will show the same number of each type of atom on each side of the equation.

1. How many atoms are in a hydrogen molecule (H2)?

2. How many atoms are in an oxygen molecule (O2)?

To set up an equation in the Chemical Equations Gizmo™, type the chemical formulas into the text boxes of the Gizmo. First, type in “H2+O2” in the Reactants box and “H2O” in the Products box. This represents the reaction of hydrogen and oxygen gas to form water.

1. Check that the Visual display is chosen on each side of the Gizmo, as well as the Atom count.

A. How many hydrogen atoms are on the Reactants side?       Products side?

B. How many oxygen atoms are on the Reactants side?       Products side?

2. Based on what you see, is this equation currently balanced?

3. Now check the Show if balanced box at the bottom, does it confirm your answer?

Continue to the next page.

Activity B: Balancing equations

Get the Gizmo ready: · Erase the chemical formulas in each text box.

Introduction: In a chemical reaction, the reactants are the substances that enter into the reaction, and the products are the substances that are made in the reaction. A chemical reaction is balanced if the numbers of reactant atoms match the numbers of product atoms.

Goal: Learn to balance any chemical equation.

1. Balance: To balance a chemical equation, you are not allowed to change the chemical formulas (that is, the subscripts) of the substances involved in the reaction. You are allowed to change the number of molecules of each substance by adding coefficients in front of the formulas.

A. To balance the oxygen atoms, add a “2” in front of the “H2O” in the Products box.

How many oxygen atoms are found on each side of the equation now?

B. To balance the hydrogen atoms, add a “2” in front of the “H2” in the Reactants box.

How many hydrogen atoms are found on each side of the equation now?

C. Is this equation currently balanced?       Click Show if balanced to check.

D. Write the balanced equation here:       H2 +       O2       H2O (remember that the number 1 is not written – there is a 1 in front of the O2 but it is unwritten)

2. Apply: Now enter a more complex chemical reaction: Ca(OH)2 + HBr CaBr2 + H2O. List the numbers of each element in the tables below:

Reactants

Ca	O	H	Br

Products

Ca	O	H	Br

A. Which elements are out of balance?

B. Add coefficients to balance first the bromine (Br) and then the hydrogen (H) atoms. When the equation is balanced, write the complete formula below:

Ca(OH)2 +       HBr       CaBr2 +       H2O

(Activity B continued on next page)

3. Practice: Balance each equation, using the Gizmo for help. The font here is Garamond 14 so you can see the difference between I, l and 1.

a)       Na +       O2       Na2O

b)       Sr +       P4       Sr3P2

c)       Cu +       Zn(NO3)2       CuNO3 +       Zn

d)       NaClO3       NaCl +       O2

e)       LiNO3       LiNO2 +       O2

f)       NH4NO3       N2O +       H2O

g)       KI +       Cl2       KCl +       I2

h)       Na +       H2O       NaOH +       H2

i)       Ca +       O2       CaO

j)       Al +       CuO       Al2O3 +       Cu

k)       MgCO3       MgO +       CO2

l)       Ga +       HCl       GaCl3 +       H2