1. LAB 5-MASS to MOLE to MASS STOICHIOMETRY
OVERVIEW:
At this time, your product is drying and therefore you cannot measure the EXPERIMENTAL or MEASURED mass in grams. The water would add mass and would cause you to overestimate the mass of your product, PbCr2O7(s). Please note water is not in the reaction, it is the solvent and does not interact chemically. You can however calculate your THEORETICAL YEILD, the mass of product you SHOULD have collected in your filter paper cone.

2. OVERVIEW CONTINUED:
The calculation is performed in three steps
CONVERT THE GIVEN OR KNOWN TO MOLES.
RATIO MOLES OF GIVEN TO MOLES OF OBJECTIVE.
CONVERT MOLES OF OBJECTIVE TO GRAMS, THEN COMPARE IT TO WHAT YOU ACTUALLY COLLECTED AND MEASURED IN LAB.

3. FLOWCHART OF THE THEORETICAL CALCULATION
Step # 1
CONVERT REACTANT(KNOWN) TO MOLES
MOLES KNOWN = MASS (GRAMS)
MOLAR MASS
Step # MOLE RATIO
(FROM REACTION)
KNOWN COEFFICIENT KNOWN = MOLES KNOWN
OBJECTIVE . COEFFICIENT OBJ MOLES OBJ. (X)
Step #3
CONVERT KNOWN REACTANT TO MOLES
MOLES OBJ. = MASS (GRAMS) (X)
MOLAR MASS

4. Step # 1
CONVERT KNOWN REACTANT Pb(NO3)2 TO MOLES
MOLES KNOWN = MASS used = g = mol
MOLAR MASS g/mol Pb(NO3)2
Step # MOLE RATIO
(COEFFICIENT, from reaction)
KNOWN : = COEFFICIENT KNOWN = MOLES KNOWN
OBJECTIVE: COEFFICIENT OBJ MOLES OBJ. (X)
Pb(NO3) = = mol = X =
PbCr2O7(s) X mol
Step # 1 CONVERT OBJECTIVE TO MASS IN GRAMS.
MOLES OBJ. = MASS (GRAMS) = = X grams = 1.438g
PbCr2O MOLAR MASS g/mol

5. CALCULATION OF MOLAR MASS of K2Cr2O7
LIST SUBSCRIPTS
MULTIPLY
By atomic mass
INSERT ATOMIC MASS
FROM PERIODIC TABLE K 2 X
39.09 g/MOL =
78.18 g Cr
51.99 g/MOL = g O 7
15.99 g/MOL = g
LIST
ELEMENTS
HERE
g/mol

6. The number of O atoms is 3 times 2
CALCULATION OF MOLAR MASS of Pb(NO3)2
LIST SUBSCRIPTS
MULTIPLY
By atomic mass
INSERT ATOMIC MASS
FROM PERIODIC TABLE
LIST
ELEMENTS
HERE Pb 1 X
207.2 g/MOL =
207.2 g N 2
14.00 g/MOL =
28.00g O 6
15.99 g/MOL =
95.95 g
The number of O atoms is 3 times 2
The number of N atoms is 1 times 2
g/mol

7. CALCULATION OF MOLAR MASS of PbCr2O7
LIST SUBSCRIPTS
MULTIPLY
By atomic mass
INSERT ATOMIC MASS
FROM PERIODIC TABLE
LIST
ELEMENTS
HERE Pb 1 X
207.2 g/MOL =
207.2 g Cr 2
51.99 g/MOL = g O 7
15.99 g/MOL = g
The number of O atoms is 7
The number of Cr atoms is 2
g/mol