1. Emp/Mol Practice

2. Agenda Go over % Comp HW Drill – Mole Conversion/% Comp
Pass back Check for Understanding
Case #7 – Emp/Mol Formula Practice
Procedure Writing
Write Procedure for Hydrate Lab

3. How many moles of oxygen gas are in 820 mg?

4. 820 mg O2
1 g O2
1 mol O2
1000 mg O2
32.0 g O2
= mol O2
**Need 2 Sig Figs
**Remember that the zeros in the front are NOT Significant
**Did you include all UNITS and CHEMICALS??

5. How many molecules of nitrogen gas are in 29.0 liters of nitrogen gas?

6. = 7.79 x 1023 molecules N2 29.0 L N2 1 mol N2 6.02 x 1023 molecules N2
**Need 3 Sig Figs
**Did you include all UNITS and CHEMICALS??

7. What is the percent of water in MgSO4  7H2O Round to the nearest hundredth

8. Molar mass = 24.3 + 32.1 + 16.0(4) + 1.0(14) + 16.0(7) = 246.4 g/mol
% H2O = (7) = x 100 = 51.14%

9. What is the difference between empirical and molecular formula?
Empirical = ratio
Molecular = true formula

10. Which of the following is NOT an empirical formula?
Na2SO4
C6H5Cl
N2H4
Sn3(PO4)4
C – able to reduce it to NH2

11. An unknown compound has a molar mass of 64
An unknown compound has a molar mass of 64.0 g/mol and has a percent composition by mass of 75% carbon and 25% hydrogen. Determine the molecular formula.

13. Now… more practice
If you DID NOT finish the video for HW, watch it now (and complete practice later)
If you DID watch the video… time to solve a possible murder case!

14. Tony demoy case
You have 30 minutes to determine who and what killed Tony DeMoy by:
Calculating the empirical and molecular formulas for each scenario
Researching the substance you calculated to determine if the information in each scenario is correct

15. Mass the double bubble
Record the mass
Chew the bubble gum until no flavor
Mass the chewed double bubble
Divide the mass of the chewed by the unchewed. This is the percent that’s not sugar, so subtract it from 1 to find the percent sugar.

16. Hydrate lab procedure
See info sheet! 