What is the % composition of carbon in benzene (C6H6)?

2 slide

Total mass of carbon/Total mass of compound

92%

How many grams of hydrogen are present in a 10.0 g sample of

benzene (C6H6)?

2 slides

1) 8% Hydrogen 2) 0.08 x 10.0 g =

0.800 g

What is the empirical formula for a compound that is 44% C, 26% N, & 30% O?

3 slides

1) Assume 100.0 g, so % is changed to grams.2) Convert each to moles by dividing by molar mass.3) Divide each mole quantity by smallest mole quantity. (Rounding may occur.)

C2NO

A compound has the empirical formula CH2O and molar mass of

120.0 g. What is its molecular formula?

3 slides

1) Mass of CH2O = 30 g/mol2) 120/30 = 43) 4(CH2O) =

C4H8O4

What is the molarity of a solution that contains 104.4 g KCl in 250 mL?

3 slides

1) Convert mass to moles 104.4 g KCl x (1 mol/74.4 g) = 1.40 mol KCl2) Convert mL volume to L250 mL x (1 L/1000 mL) = 0.25 L3) Divide moles/volume =

5.67 M

What mass of KCl is dissolved in 500.0 mL to produce 2.50 M solution?

3 slides

1) Convert mL volume to L (0.5000 L)2) Solve for moles0.5000 L x (2.50 mol/L) = 1.25 mol3) Convert moles to grams1.25 mol x (74.4 g/mol) =

93 g

How many moles of CO2 are in 22.0 g?

2 slides

22.0 g x (1 mol/44.0 g) =

0.500 mol

How many moles of O2 are in 5.6 L?

2 slides

5.6 L x (1 mol/22.4 L) =

0.25 mol

What is the volume occupied by 56.0 g of N2 ?

3 slides

56.0 g x (1 mol/28.0 g) x (22.4 L/mol) =

44.8 L

What is the density of O2 ?

2 slides

32.0 g/ 22.4 L =

1.43 g/L

What is the molar mass of a gas that has a density of 2.25 g/L?

2 slides

(22.4 L/1 mol) x (2.25 g/L) =

50.4 g/mol

Use the following reaction:4NH3 + 3O2 2N2 + 6H2O

How many moles of oxygen, with excess ammonia, can produce 4 moles of nitrogen?

2 slides

4 mol N2 x (3 mol O2 /2 mol N2) =

6 mol O2

Use the following reaction:4NH3 + 3O2 2N2 + 6H2O

How many grams of ammonia are needed to produce 14.0 g of N2?

3 slides

14.0 g N2 x (1 mol N2/28 g) x (4 mol NH3 /2 mol N2 ) x (17 g/1 mol) =

17.0 g

Use the following reaction:4NH3 + 3O2 2N2 + 6H2O

How many grams of water are produced from 44.8 L of O2?

4 slides

44.8 L x (1 mol O2 /22.4 L) x (6 mol H2O/3 mol O2) x (18 g H2 O/1 mol) =

72.0 g

Use the following reaction:4NH3 + 3O2 2N2 + 6H2O

If there are 5.00 moles of ammonia and 5.00 moles of oxygen, how many moles of nitrogen are produced?

4 slides

1) 5.00 moles of each reactant is what you have2) 5.00 mol NH3 x (3 mol O2 /4 mol NH3 ) = 3.75 mol O2

is what I need3) O2 : have (5.00 mol) > need (3.75 mol), so NH3 is limiting reactant4) 5.00 mol NH3 x (2 mol N2 / 4 mol NH3 ) =

2.50 mol N2

Use the following reaction:4NH3 + 3O2 2N2 + 6H2O

If excess oxygen reacts with 3.00 mol NH3 , what is the theoretical yield of H2O?

3 slides

3.00 mol NH3 x (6 mol H2O/4 mol NH3) x (18 g/mol) =

81.0 g

If 70.0 g of water is produced, what is the percent yield?

2 slides

1) 70.0 g = actual yield2) 81.0 g = theoretical yield3) [actual/theoretical] x 100 =

86.4 %

Use the following reaction:Fe + 2HCl FeCl2 + H2

If 20 atoms of iron are dropped into a beaker containing hydrochloric acid, how many molecules of hydrogen would be produced?

2 slides

20 Fe atoms x (1 H2 molecule/1 Fe atom) =

20 H2 molecules