1.27 #16 Find the mass in grams of 4.52 x 10

#16 Find the mass in grams of 4.52 x 10-3 moles of C20H42 Mult. by Molar Mass

4.52 x 10-3 moles 1

X

282.0 g 1mole

=

1.27

grams

#17 Calculate the mass in grams of 2.5 moles of Iron (II) hydroxide Fe(OH) Mult. by Molar Mass

2.5 moles 1

X

89.8.0 g 1mole

=

225

2

grams

#18 Find the number of moles in 3.70 x 10-1 (.370) grams of boron

B 10.8

divide by Molar Mass

3.70 x 10-1 grams 1

X

1 mole B = 10.8 g

.0343

moles

#19 Calculate the number of moles in 75.0 g of dinitrogen trioxide

N2O3

= 76.0g/mole

divide by Molar Mass

75 g 1

X

1 mole 76.0 g

=

.99

moles

20. What is the volume of these gases at standard temperature and pressure? (STP) mult. by 22.4

a. 3.20 x 10-3 moles CO2 3.20 x 10-3mol 1

22.4 liters 1 mole

x

b. 3.70 moles N2 3.7 mole N2 1

x

22.4 liters 1 mole

=.0717 liters

for most gases: 22.4 Liters 1 mole

82.9 liters N 2 =

21. At STP (standard temp. and pressure), what volume do these gases occupy? mult. by 22.4

a. 1.25 moles He 1.25 mol 1

22.4 liters 1 mole

x

b. .335 moles C2H6 .335 mole C2H6 1

x

22.4 liters 1 mole

for most gases: 22.4 Liters 1 mole =28.0 liters He

7.5 liters C H 2 6 =

22. A gaseous compound composed of sulfur and oxygen, which is linked to the formation of acid rain, has a density of 3.58 g/liter at STP. What is the molar mass of this gas? We are given the gas in units of g/liter and need to find the molar mass which is in units of g/mole. Therefore we need to use the relationship between liters and moles (22.4 liters/mole) to solve this:

3.58 g 1 liter

x

22.4 liters = 1 mole

80.2? g 1 mole

23. What is the density of krypton gas at STP? Krypton has like all normal gases 22.4 liters/mole at STP. Therefore, knowing this and the molar mass of krypton (from the periodic table) we solve as follows?

83.8 g Kr x 1 mole

1 mole = 22.4 liters

3.74?

g 1liter

24. Describe how to convert between the mass and the number of moles of a substance divide. by Molar Mass

multiply by Molar Mass

To go from grams to moles you need to divide by the molar mass To go from moles to grams you need to multiply by the molar mass

25. What is the volume of one mole of any gas at STP? 22.4 Liters 1 mole

26. How many grams are in 5.66 moles of CaCO3? 5.66 moles x 100.1 g 1 1 mole

= 567 g CaCO3

27. Find the number of moles in 508 g of ethanol (C2H6O)?

C2H6O

= 46.0g/mole

508 grams x 1

1 mole 46.0 g

= 11.0 moles

28. Calculate the volume, in liters, of 1.50 mol of Cl2 at STP. 1.5 moles 1

x

22.4 liters 1 mole

= 33.6 liters

29. The density of an elemental gas is 1.7824 g/liter at STP. What is the molar mass of the element?

1.7824 g 1liter

x

22.4 liters 1 mole

= 39.9 g 1 mole

30. The densities of gases A,B,and C are 1.25 2.86 and 0.7134 respectively. Calculate the molar mass of each substance. Identify each substance as ammonia, sulfur dioxide, chlorine, nitrogen, or methane.

SO2

1.25 g x 22.4 liter = 1 liter 1 mole

= 64.1g/mole

28g mole

Cl2

= 71.0g/mole

NH3

= 17.0g/mole

N2

= 28.0g/mole

CH4

= 16.0g/mole

30. The densities of gases A,B,and C are 1.25 2.86 and 0.7134 respectively. Calculate the molar mass of each substance. Identify each substance as ammonia, sulfur dioxide, chlorine, nitrogen, or methane.

SO2

2.86 g x 22.4 liter = 1 liter 1 mole

64.1g mole

= 64.1g/mole

Cl2

= 71.0g/mole

NH3

= 17.0g/mole

N2

= 28.0g/mole

CH4

= 16.0g/mole

30. The densities of gases A,B,and C are 1.25 2.86 and 0.7134 respectively. Calculate the molar mass of each substance. Identify each substance as ammonia, sulfur dioxide, chlorine, nitrogen, or methane. 0.7134 g x 22.4 liter = 1 liter 1 mole

16.0g mole

NH3

SO2

= 17.0g/mole

Cl2

N2

= 64.1g/mole

= 71.0g/mole

= 28.0g/mole

CH4

= 16.0g/mole

31. Three balloons filled with three different gaseous compounds each have a volume of 22.4 L at STP. Would these balloons have the same mass or contain the same number of molecules? Explain

They would have the same number of molecules because the rule states that equal volumes of gases contain equal numbers of molecules. The masses are probably different depending on the molar mass of each gas.