Conversion
Combustion Analysis
Empirical/Molecular Formula
100

How many moles of potassium fluoride (KF) are in a 32.8 g sample?

0.56 moles of KF

100

What is combustion analysis?

When we burn a hydrocarbon, collect the resulting CO2 and H2O, and use their masses to find out the empirical formula of the hydrocarbon we burned.

100

What would be the empirical formula for the compound with the molecular formula C3H9Cl3?

CH3Cl

200

How many moles are 3.7 x 1025 copper ions?

6.15 x 101 moles or 61.5 moles

200

An unknown hydrocarbon is burned in oxygen and produces 7.335 g of CO2 and 4.5 g of H2O, what is the empirical formula of the unknown hydrocarbon?

CH3

200

What would be the molecular formula for a compound with the empirical formula of CH2 if its molar mass is 42.09 g/mol?

42.09/14.03 = 3

C3H6

300

How many molecules are there in 24.5 grams of water?

8.18 x 1023 molecules

300

A hydrocarbon is burned. 26.41 grams of COand 21.62 grams of H2O were produced.  What is the empirical formula of the compound you burned?

CH4

300

What is the percent composition of the empirical formula H2O2Br?

H: 2.02

O: 32

Br: 79.5

total = 113.52

H: 1.78%    O:  28.19%    Br:  70.03%  


400

A sample contains 5.32 x 1022 molecules C3H6O2.  What is the mass of the sample?

6.55 grams

400

A hydrocarbon is burned. 28.17 grams of COand 8.65 grams of H2O were produced.  What is the empirical formula of the compound you burned?

C2H3

400
What is the empirical formula of a compound that has a percent by pass of:

H: 2.06%   S:  32.69%     O: 65.25%  

H2SO4

500

A sample of contains 241 g of Ba(NO­2)2.   How many nitrogen atoms are present in the sample?

Step 1: Convert grams to particles of Ba(NO­2)2

6.33 x 1023 p

Step 2: Multiply by the number of N's in the formula Ba(NO­2)2

6.33 x 1023 p x 2 

= 1.27 x 1024 p N


500

A hydrocarbon is burned. 1.956 grams of COand 3.003 grams of H2O were produced.  What is the empirical formula of the compound you burned? (try to keep at least 3 sig figs for this)

C2H15


500

The percent composition of a compound is 40% carbon, 6.73% hydrogen, and 53.28% oxygen.  The molar mass of the molecular formula is 180 g/mol. What is the molecular formula of the compound?

Empirical Formula: CH2O

Molecular Formula: C6H12O6

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