Stoichiometry - DP1

Empiric formula

100

In a sample are found 1.33 moles of N (nitrogen) and 2 moles of O (oxygen). what is the empirical formula?

N₂O₃

200

Analysis of 15 grams of a compound shows that it consists of 6g carbon, 1g hydrogen and 8g oxygen. What is the empirical formula?

CH₂O

n(C)=6/12=0.5        /:0.5

n(H)=1/1=1            /:0.5

n(O)=8/16=0.5        /:0.5

300

What is the molecular formula of a compound that consists of only carbon and hydrogen in a ratio of 1:1, and has a molar mass of 78 g/mol?

78/(1+12)=6

C₆H₆

400

The empirical formula consists of elements X and Y. A_r(X)=20  A_r(Y)=15. The sample consists of 40% element X. what is the empirical formula?

XY₂

n(X)=40/20=2    /:2

n(Y)=60/15=4     /:2

500

A 0.30 g sample of a compound containing carbon, hydrogen and oxygen undergoes complete combustion to produce 0.66 g of CO₂ and 0.36 g of H₂O. Determine the empirical formula of the compound.

C₃H₈O

Stoichiometry

100

How many moles of O₂ are produced by reacting 12 moles of KClO₃? 

2KClO₃--->2KCl+3O₂ 

18 moles

200

What mass of CO₂ would be produced from combustion of 2 moles ethanol (C₂H₅OH)? 

C₂H₅OH + 3O₂ --> 2CO₂ + 3H₂O

4x44=176g CO₂

300

How much CO₂ (in mass) would be produced from combustion of 11.5g ethanol (C₂H₅OH)? 

C₂H₅OH + 3O₂ --> 2CO₂ + 3H₂O

22g of CO₂

400

4 balloons with a the same volume contain 0.05 mole of gas: Ar, He, H₂ and C₃H₈. Which one is the heaviest?

C₃H₈

500

3H_2(g)+N_2(g)-->2NH_3(g)   

60cm³ of H₂ reacted with 20cm³ of N_2. What volume of NH₃ was produced?

40cm³ NH_3(g)

Limiting reactant and % yield

100

3H_2(g)+N_2(g)-->2NH_3(g),   

3 mol H₂ is reacted with 6 mol N₂. Which is the limiting reactant?    

H₂

200

160g N₂H₄ is mixed with 160g N₂O_4. Which is the limiting reactant?    

2N₂H_4(l)+N₂O_4(l)-->3N_2(g)+4H₂O_(l)     

N₂O₄

300

Fe₂O_3(s)+3CO_(g)-->2Fe(g)+3CO₂          

224g of CO is available to react with 400g Fe₂O₃. How much iron is produced?

279g Fe

400

In the reaction 2NH₃+3CuO-->N₂+3Cu+3H₂O, 34g NH₃ reacted with 340g CuO. 152g of copper were produced. What is the %yield of the reaction?

80%

500

2NH₃+3CuO-->N₂+3Cu+3H₂O

34g NH₃ reacted with 340g CuO. Under different conditions, the %yield of the reaction is 90%. How much copper would be produced?

171g Cu

Significant figures

100

How many significant figures are in the number 520?

2

200

How many significant figures are in number 0.00320

3

300

What is the sum of 3.33+10.666

14.00

400

what is the area of a rectangle that its width is 5.55 cm and its length is 1.0 cm?

5.6 cm²

500

Density is calculating by division of a mass/volume. A solvent of mass 5.00 g has a volume of 2.2 cm³. What is the density of the solvent?

2.3 g/cm³