3.2.2 Introducing Conversions of Masses, Moles, and Number of Particles

Question 1

Introducing Conversions of Masses, Moles, and Number of Particles

Answer 1

• The molar mass of a substance represents the mass of one mole of that substance.
• The molar mass of a substance can be used as a conversion factor between mass and moles.

Question 2

elements, periodic table, molecule

Answer 2

• The molar mass of a substance represents the mass of one mole of that substance. The molar masses of elements can be found on the periodic table.
• For example, the molar mass of fluorine (F) is 18.998403 g/mol. One mole of fluorine has a mass of 18.998403 g.
• Molar masses are additive. To find the mass of one mole of potassium fluoride (KF), simply add together the masses of potassium and fluoride. The molar mass of potassium fluoride is 58.0967 g/mol.
• The molar mass of a more complex molecule such as ethanol (C2H5OH) can be found by multiplying the number of atoms of each element by the element’s molar mass and summing these individual masses.
• The molar mass of ethanol is 46.069 g/mol. The molar mass of a substance can be used as a conversion factor between mass and moles.
• For example, to find the mass of 0.9628 moles of iron, simply multiply 0.9628 mol by the molar mass of iron (55.845 g/mol).
• Notice that the mass of 0.9628 moles of iron is lower than the mass of one mole of iron. This makes sense, because 0.9628 is less than one.

Question 3

How many sodium ions are in 25.75 grams of table salt (sodium chloride)?

Answer 3

2.653 × 10^23 sodium ions

Question 4

What mass does 2.30 moles of iron represent?

Answer 4

128 grams

Question 5

How could you measure 3.00 moles of water?

Answer 5

by weighing 54.0 grams of water

Question 6

What is the molar mass of sulfuric acid (H2SO4 )?

Answer 6

98.076 g / mole

Question 7

What is the molar mass of ethanol (C2H6O)?

Answer 7

46.064 grams / mole

Question 8

What mass does 0.876 moles of hydrogen peroxide (H2O2 ) represent?

Answer 8

29.8 grams

Question 9

How many molecules are there in 29.777 grams of hydrogen peroxide (H2O2 )?

Answer 9

5.2701 × 10^23 molecules hydrogen peroxide

Question 10

In the portion of the periodic table shown, what does the number 12.0107 represent?

Answer 10

molar mass

Question 11

What is the reason that conversion from grams to moles is useful?

Answer 11

Balanced chemical reactions relate to moles of reactant molecules, not to masses of reactant molecules

Question 12

Which of the following statements is not true?

Answer 12

One gram of water consists of two grams of hydrogen and one gram of oxygen.