Chapter_7_Powerpoint 2022

Question 1

What is the formula mass?

Answer 1

The mass of a single molecule or formula unit

Example: The formula mass of a water molecule (H2O) is calculated as 2(1.01 u) + 1(16.00 u) = 18.02 u.

Question 2

How do you calculate the percent composition of one element in a compound?

Answer 2

Percent composition = (mass of one element / mass of compound) x 100%

Example: For octane (C8H18), the percent composition of carbon is 84.09% and hydrogen is 15.91%.

Question 3

What technique is used to measure the mass of molecules?

Answer 3

Mass spectrometry

This technique measures the mass of molecules by ionizing chemical species and sorting them based on their mass-to-charge ratio.

Question 4

What is Avogadro’s Number?

Answer 4

6.02 x 10^23 units

This number is used to relate moles to particles, such as atoms or molecules.

Question 5

How many grams are in one mole of carbon?

Answer 5

12.01 grams

The molar mass of carbon is equivalent to its atomic mass in grams.

Question 6

What is the relationship between grams, moles, and particles?

Answer 6

Moles relate atoms to grams and particles

For example, 1 mole of CO2 (44.01 g) contains 6.02 x 10^23 molecules.

Question 7

Differentiate between theoretical yield and actual yield.

Answer 7

Theoretical yield is the maximum amount of product that can be produced, while actual yield is the amount actually obtained from a reaction

Percent yield is calculated using the formula: (actual yield / theoretical yield) x 100%.

Question 8

What is the formula mass of potassium carbonate (K2CO3)?

Answer 8

138.21 u

It is calculated as 2(39.10 u) + 1(12.01 u) + 3(16.00 u).

Question 9

What is the percent yield if the theoretical yield is 50 g and the actual yield is 40 g?

Answer 9

80%

Percent yield = (40 g / 50 g) x 100%.

Question 10

Fill in the blank: 1 atomic mass unit (u) = ______ g.

Answer 10

1.66 x 10^-24 g

Question 11

What is the percent composition of hydrogen in water (H2O)?

Answer 11

11.19%

The calculation is based on the formula mass of water, which is 18.02 u.

Question 12

What is the limiting reagent in a chemical reaction?

Answer 12

The reactant that is completely consumed first, limiting the amount of product formed

It determines the maximum yield of the reaction.

Question 13

How do you convert grams of a substance to moles?

Answer 13

Use the formula: grams / molar mass

For NaCl, if you have 305 g, you divide by its molar mass (58.44 g/mol) to find moles.

Question 14

Fill in the blank: The formula mass of carbon dioxide (CO2) is ______ g.

Answer 14

44.01 g

Question 15

What is the mass in grams of 2.53 x 10^23 iron atoms?

Answer 15

23.5 grams Fe

Calculated using the relationship between atoms and moles, and then converting moles to grams.

Question 16

True or False: The actual yield can never exceed the theoretical yield.

Answer 16

True

Question 17

What is the mole ratio of H2 to O2 in the combustion of methane (CH4)?

Answer 17

2:1

The balanced equation is CH4 + 2 O2 → CO2 + 2 H2O.

Question 18

What is the molar mass of NaCl?

Answer 18

58.44 g/mol

Question 19

What is stoichiometry?

Answer 19

Using the amount of one material to predict the amount of another based on the balanced equation

It involves calculations using molar ratios from balanced chemical reactions.

Question 20

Fill in the blank: The formula mass of magnesium oxide (MgO) is ______ g.

Answer 20

40.30 g

Question 21

What does the term ‘excess reagent’ refer to?

Answer 21

The reactant that is not completely consumed in a reaction

It remains after the limiting reagent is used up.

Question 22

How many grams of MgO can be produced from 5.24 g of MgCO3?

Answer 22

2.51 g

Calculation uses the stoichiometry of the reaction and molar masses.

Question 23

What is the theoretical yield of a reaction?

Answer 23

The calculated maximum amount of product that can be formed from given reactants

Question 24

What is the limiting reagent when 1.2 moles of potassium reacts with 15 moles of chlorine gas?

Answer 24

K is the limiting reagent

K is completely consumed, limiting the amount of product formed.

Question 25

What is the excess reagent when 1.2 moles of potassium reacts with 15 moles of chlorine gas?

Answer 25

Cl2 is the excess reagent ## Footnote Cl2 is not completely consumed, leaving some leftover after the reaction.

Question 26

How many moles of potassium chloride can be produced from 1.2 moles of potassium?

Answer 26

1.2 moles KCl ## Footnote Based on the reaction 2 K + Cl2 → 2 KCl.

Question 27

How many moles of potassium chloride can be produced from 15 moles of chlorine gas?

Answer 27

30 moles KCl ## Footnote Based on the stoichiometry of the reaction.

Question 28

What is the limiting reagent when 30 moles of uranium react with 75 moles of fluorine gas?

Answer 28

F2 is the limiting reagent ## Footnote F2 limits the amount of UF6 that can be produced.

Question 29

How many moles of UF6 can be produced from 30 moles of uranium?

Answer 29

30 moles UF6 ## Footnote Based on the reaction U + 3 F2 → UF6.

Question 30

How many moles of UF6 can be produced from 75 moles of F2?

Answer 30

25 moles UF6 ## Footnote Based on the stoichiometry of the reaction.

Question 31

Using the recipe, how many turkey-and-cheese sandwiches can be made with 80 slices of bread, 18 slices of turkey, and 15 slices of cheese?

Answer 31

15 sandwiches ## Footnote Limited by the number of cheese slices.

Question 32

What is the theoretical yield?

Answer 32

The amount of a product that can form, based on the balanced equation ## Footnote It is a calculated value, not the actual yield observed.

Question 33

What is the actual yield?

Answer 33

The amount actually obtained ## Footnote This is the measured amount after a reaction.

Question 34

How is percent yield calculated?

Answer 34

Percent yield = (Actual yield / Theoretical yield) × 100% ## Footnote This formula helps assess the efficiency of a reaction.

Question 35

What can cause the actual yield to be lower than the theoretical yield?

Answer 35

Material sticks to container walls, unwanted side products, product lost during purification ## Footnote These factors reduce the amount of product obtained.

Question 36

What is the percent yield for a reaction with a theoretical yield of 240 grams and an actual yield of 180 grams?

Answer 36

75% ## Footnote Calculated as (180 g / 240 g) × 100%.

Question 37

What is the theoretical yield of SF6 from 120.0 kg of sulfur reacting with excess fluorine gas?

Answer 37

546.7 kg SF6 ## Footnote Based on the stoichiometry of the reaction S + 3F2 → SF6.

Question 38

What was the percent yield for the production of SF6 if 480.2 kg was isolated?

Answer 38

87.84% ## Footnote Calculated as (480.2 kg / 546.7 kg) × 100%.

Question 39

What is the theoretical yield of magnesium oxide from 5.25 grams of MgCO3?

Answer 39

To be calculated based on stoichiometry ## Footnote Requires the balanced equation MgCO3 → MgO + CO2.

Question 40

What is the percent yield if 2.37 grams of MgO are obtained from the reaction starting with 5.25 grams of MgCO3?

Answer 40

To be calculated based on theoretical yield ## Footnote Requires the theoretical yield value to compute.

Question 41

What is the percent yield for a reaction starting with 14.2 g of C6H6 and isolating 13.7 g of C6H5Br?

Answer 41

To be calculated based on theoretical yield ## Footnote Requires the theoretical yield value to compute.