step 5
write the chemical equation

1c1h4 (g) + 1o2 (g) 1c1o2 g) + 1h201 (g)

write subscripts to indicate states of matter (s, l,g, aq)

step 6
add up atoms of each element in reactants and products

reactants
c = 1 x 1 = 1 atom
h = 1 x 4 = 4 atoms
o = 1 x 2 = 2 atoms
hint: multiply your coefficient by your subscript for each element

products
c = 1 x 1 = 1 atom
h = 1 x 2 = 2 atoms
o = (1 x 2) + (1 x 1) = 3 atom

step 7
answer y/n: are the # of atoms of each type of element balanced in the reactants and products?

step 8
if yes: you are done move to step 10
if no: add coefficients to your chemical equation to balance atoms.

ch4 (g) + 2o2 (g) co2 g) + 2h20(g)

hint:
never never never change subscripts in chemical formulas to add more atoms
–e. g. ch4 can’t become c2h5 – that is a different molecule than methane.
only change coefficients to add more atoms/molecules.)

step 9
draw an updated representation to match your balanced chemical equation

step 10
describe balanced chemical reaction/drawing in terms of individual particles:
1 molecule of ch4 reacts with 2 molecules of o2 to form 1 molecule of co2 and 2 molecules of h20

step 11
describe balanced chemical reaction/drawing in terms of moles
1 mole of ch4 reacts with 2 moles of o2 to form 1 mole of co2 and 2 moles of h20

step 12
explain: how does your chemical equation and picture demonstrate the conservation of particles?

in my chemical equation and in my picture, i can see that:
in reactants:
c = 1 atom
h = 4 atoms
o = 4 atoms

in products:
c = 1 atom
h = 4 atoms
o = 4 atoms

therefore, the number of atoms of each element is balanced in the reactants and products and shows conservation of particles.

step 13
explain: how does your chemical equation and picture represent conservation of mass?

hint: you need to prove using molar mass that mass of reactants = mass of products

ch4:

molar mass of ch4: 12.01 + (4)(1.01) = 16.05 grams

o2:

molar mass of o2: (2)(16.00) = 32.00 grams

there are 2 moles of o2 in the balanced chemical equation so: 32.00 grams/mole x 2 moles = 64.00 grams

total mass of reactants: 16.05 + 64.00 = 80.05 grams

co2

molar mass of co2: (12.01 + (2)(16.00) = 44.01 grams

h20

molar mass of h20: (2)(1.01) + 16.00 = 18.02 grams

there are 2 moles of h20 in the balanced chemical equation so: 18.02 grams/mole x 2 moles = 36.04 grams

total mass of products: 44.01 + 36.04 = 80.05 grams

therefore, the total mass of the reactants is equal to the total mass of the products and shows conservation of mass.

your turn:

/ 20 points

step 1
you will be given: word description
chlorine gas reacts with solid sodium bromide to form solid sodium chloride (salt! ) and bromine gas

step 2
you will be given: chemical formulas of each reactant(s) and product(s)
cl2 (g) nabr(s) nacl(s) br2(g)

step 3
create a key

step 4
draw representative particles for each reactant and product
reactants

products

step 5
write the chemical equation

step 6
add up atoms of each element in reactants and products
reactants

products

step 7
(1 pts)
answer y/n: are the # of atoms of each type of element balanced in the reactants and products?

step 8
(2 pts)
if yes: you are done move to step 10

if no: add coefficients to your chemical equation to balance atoms.

step 9
(2 pts)
draw a representation to match your balanced chemical equation

step 10
(1 pt)
describe balanced chemical reaction/drawing in terms of individual particles:

step 11
(1 pt)
describe balanced chemical reaction/drawing in terms of moles

step 12
(2 pts)
explain: how does your chemical equation and picture demonstrate conservation of particles?

in my chemical equation and in my picture, i can see that:

step 13
(4 pts)
explain: how does your chemical equation and picture represent conservation of mass?

in my chemical equation and in my picture, i can see that: