Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

# Making 2 grams of a compound

HOW TO OBTAIN 2.00 g OF A COMPOUND

Pre-Lab Questions:

Copy the following word equations and chemical equations IN NUMERICAL ORDER in your lab notebook.

Calculate the masses reacting in each one and then calculate how many grams of reactants you will need to prepare 2 g of precipitate:

Reactant pair #1

zinc sulfate heptahydrate +  Calcium acetate monohydrate   ==>  calcium sulfate +  zinc acetate    +   water

ZnSO4•7H2O          +          Ca(CH3COO)2•H2O      ==>      CaSO4 (s)      +  Zn(CH3COO)2 +   8H2O

Reactant pair #2

zinc sulfate heptahydrate   +  Sodium carbonate     ==>     zinc carbonate   +   sodium sulfate   +    water

ZnSO4•7H2O          +             Na2CO3         ==>         ZnCO3(s)      +      Na2SO4         +     7H2O

Reactant pair #3

zinc sulfate heptahydrate     +     Calcium Chloride dihyrate  ==>     calcium sulfate   +    zinc chloride  +  water

ZnSO4•7H2O          +             CaCl2•2H2O         ==>          CaSO4        +        ZnCl2       +   9H2O

Reactant pair #4

zinc sulfate heptahydrate     +    potassium carbonate   ==>     zinc carbonate    +  sodium sulfate +  water

ZnSO4•7H2O          +             K2CO3             ==>         ZnCO3(s)      +      K2SO       +   7H2O

Reactant pair #5

magnesium sulfate heptahydrate + Calcium acetate monohydrate  ==> calcium sulfate +  magnesium acetate  +  water

MgSO4•7H2O                 +           Ca(CH3COO)2•H2O       ==>        CaSO4     +    Mg(CH3COO)2     +  8H2O

Reactant pair #6

magnesium sulfate heptahydrate  +   Sodium carbonate   ==>     magnesium acetate    +  sodium sulfate  +  water

MgSO4•7H2O                 +          Na2CO3           ==>               MgCO3(s)      +      Na2SO4      +  7H2O

Reactant pair #7

magnesium sulfate heptahydrate  +   Calcium Chloride dihyrate   ==>     calcium sulfate    +  Magnesium chloride +  water

MgSO4•7H2O                  +          CaCl2•2H2O            ==>              CaSO4      +      MgCl2    +  9H2O

Reactant pair #8

magnesium sulfate heptahydrate  +   potassium carbonate   ==>       magnesium carbonate      +   Potassium Sulfate  +  water

MgSO4•7H2O               +            K2CO3                 ==>                      MgCO3(s)            +            K2SO4        +  7H2O

Reactant pair #9

Calcium acetate monohydrate  +  Sodium carbonate              ==>      calcium carbonate       +    Sodium acetate       +  water

Ca(CH3COO)2•H2O       +       Na2CO3                      ==>            CaCO3(s)             +       2  NaCH3COO       +   H2O

Reactant pair #10

Calcium acetate monohydrate  +  potassium carbonate   ==>      calcium carbonate       +     Potassium acetate       +  water

Ca(CH3COO)2•H2O       +       K2CO3                  ==>              CaCO3(s)           +         2  KCH3COO         +   H2O

Reactant pair #11

Sodium carbonate   +  Calcium Chloride dihyrate     ==>      calcium carbonate    +     sodium chloride     +    water

Na2CO        +       CaCl2•2H2O                 ==>            CaCO3(s)          +          2  NaCl            +     2H2O

Reactant pair #12

Calcium chloride             +  potassium carbonate         ==>      calcium carbonate   +   Potassium Chloride     +  water

CaCl2•2H2O         +          K2CO3                      ==>            CaCO3(s)            +       2  KCl      +  2 H2O

## Can You Make 2.00 Grams of a Compound?

Purpose:

Often, in chemistry, scientists are required to make a specific amount of a product.   In this lab, you will be asked to do the same thing.
You will be given two compounds to react together and then isolate a product.  Use your skills of predicting chemical reactions, balancing equations, and calculating molar mass to solve a complex stoichiometry problem.  Test your laboratory techniques by mixing the reactants and isolating exactly 2.00 g of a compound.

Materials:

• 2- plastic weighing boats
• 2 -100 cm3 beaker
• 1 – 250 cm3 beaker
• Funnel
• Paper filter
• Ring stand
• Small iron ring (to hold the funnel)
• Glass rod

Data Table:

Build two suitable data tables showing ALL your measurements.

1. Table 1: Include the weighing boat mass in your table and how you calculate the exact amount of the reactants by subtraction.
2. Table 1: Include the measurement of the filter paper and how you calculate the exact amount of the chemical you obtained by precipitation

Procedure:

Before the lab:

1. Write a balanced chemical equation for your reaction.
2. Use stoichiometry to calculate the mass of each reactant needed to produce the precipitate.
3. Use the calculated masses of reactants to make the 2.00 grams of precipitate.

During the lab:

1. Label your beakers with the formulas of the chemicals your teacher assigned you.
2. Obtain reactants from teacher using labelled papers weighing boats  (these will be in excess)
3. Measure the mass of one of the 100 mL beaker using the digital balance.
4. zero the balance.
5. Measure inside the beaker the exact amount of one of the chemicals calculated for your reactants’ pair.
6. Place the second chemical in the second beaker (this will be in excess)
7. Add 25 ml of distilled water to each beaker and check that they dissolve completely.  If any of the compounds did not dissolve completely, add 5 cmmore of distilled water and stir the solution with a glass stirring rod.
8. Combine both solution by placing the content in the excess chemical into the one that was exact.
9. Wait 5 minutes for product to form. Be sure that all the liquid in one of the beakers is transferred to the other one.
10. Use some distilled water to rinse the empty beaker and transfer the content to the one containing the liquid and precipitate.
11. Wait for 5 minutes stirring from time to time. Observe if any precipitate is formed. If not, tell your teacher.
12. Take a filter paper and measure its mass. ______
13. Place a piece of filter paper in the funnel, wetting it down to keep it stuck to the funnel.
14. Place the funnel in the flask.
15. After the two compounds have been combined, isolate the precipitate by filtering the solution.  Pour the solution into the funnel. Be careful not to let the solution flow over the funnel.
16. Wash out the beaker several times with distilled water from the squirt bottle provided.  Pour each washing into the funnel to reclaim any precipitate that may have stuck to the sides of the beaker
17. Wash the precipitate with distilled water trying to rinse the paper the best you can.
18. Let the paper filter dry with the precipitate by covering it with a piece of paper and placing it in a secure place until next class.
19. After it is completely dry, weight the paper filter and subtract the mass of the filter paper recorded in “g”.

Analysis questions

1. How many grams of reactant 1 did you use?
2.  How many grams of reactant 2 did you use?
3. How much was the theoretical yield of the reaction?
4. If you did not obtain exactly 2.00 g of the precipitate, describe at least 3 factors that affect your results.
5. How much was the percent yield of your reaction?