Chemistry A- Unit 6: Stoichiometry

If an oxyanion has two forms, which suffix does the form with fewer atoms get?

-ite

Refer to the scenario and balanced equation. 2H2 + O2 →→ 2H2O At the beginning of the reaction, it is measured that there are 15.0 g of hydrogen (H2) and 97.0 g of oxygen (O2). What is the theoretical yield for the water that will be produced in the reaction? (M H2O = 18.0 g/mol; M CH4 = 16.0 g/mol)

1.08 x 102 g H2O

How many moles of oxygen gas (O2) are in a 2.50 L container at standard temperature and pressure?

1.12 x 10-1 mol O2

How many particles are in 2.02 moles of dinitrogen monoxide (N2O)?

1.22 x 1024 particles N2O

Examine the statement and balanced equation. Pure elemental iron undergoes a single replacement reaction with sulfuric acid (H2SO4) to produce iron(III) sulfate (Fe2(SO4)3) and hydrogen gas. 2Fe + 3H2SO4 →→ Fe2(SO4)3 + 3H2(M Fe = 55.8 g/mol, M H2SO4 = 98.1 g/mol, M Fe2(SO4)3 = 399.9 g/mol, M H2 = 2.0 g/mol) If 3.21 x 1012 mol of iron(III) sulfate are formed, how many g of it will be produced?

1.28 ×× 1015 g Fe2(SO4)3

Study the balanced equation. N2 + 3H2 →→ 2NH3 How many mol of nitrogen (N) are needed to produce 3.00 mol of ammonia (NH3)?

1.50 mol N2

Study the balanced equation. C + O2 →→ CO2(M C = 12 g/mol; M CO2 = 44 g/mol) When 52.0 g of carbon dioxide (CO2) are produced, what mass of carbon is present in the product?

14.2 g C

What is the molar mass of ammonia (NH3)? (NOTE: N = 14.007 amu, H = 1.008 amu)

17.0 g/mol NH

What is the molar mass of water (H2O)? (NOTE: H = 1.008 amu, O = 15.999 amu)

18.0 g/mol

In a solution, there is 1 g of NaCl for every 5 g of water. What is the ratio of sodium to water?

1NaCl : 5H2O, because in the solution, for every 1 g of NaCl there are 5 g of H2O

Study the balanced equation. 3Mg + Fe2O3 →→ 3MgO + 2Fe What is the theoretical yield for MgO when 0.52 mol of Mg and 0.28 mol of Fe2O3 react?

2.10 x 101 g MgO

Study the chemical reaction. N2(g) + 3H2(g) →→ 2NH3(g) At the end of the chemical reaction, 5 moles of NH3 are produced. How many moles of N2 and H2 entered the reaction?

2.5 moles of N2 7.5 moles of H2

What is the molar mass of aluminum sulfate (Al2(SO4)3)? (NOTE: Al = 26.981 amu, S = 32.06 amu, O = 15.999 amu)

342.1 g/mol

Lesson 27

Finding Yields

Study the chemical reaction. 4Fe + 3O2 → 2Fe2O3 What is the mole ratio between Fe and O2?

4 Fe/3 O2

Examine the balanced equation. 2CO(g) + O2(g) →→ 2CO2(g) What is the percent yield of CO2 if the reaction of 1.00 g of CO with excess O2 produces 0.68 g of CO2? (M CO2 = 44.0 g/mol, M CO = 28.0 g/mol)

43.3%

In a chemical reaction, 10 moles of the element aluminum react with 7.5 moles of oxygen gas. This produces 5 moles of aluminum oxide (Al2O3). What is the balanced equation?

4Al + 3O2 → 2Al2O3

How many mol of NaHCO3 are in a 454 g box of baking soda (NaHCO3)? (NOTE: M of NaHCO3 = 84.0 g/mol)

5.40 mol NaHCO3

There are 175.989 g of oxygen to 22.176 g of hydrogen and 144.132 g of carbon (C) in a 342.297 g sample of sucrose (C12H22O11). What is the mass percent of oxygen in sucrose?

51.4% is oxygen.

Study the balanced equation. C + O2 →→ CO2(M O2 = 32 g/mol; M CO2 = 44 g/mol) When 78.0 g of carbon dioxide (CO2) are produced, what mass of oxygen is present in the product?

56.7 g oxygen

How many particles are in one mole of methane (CH4)?

6.02 x 1023 particles CH4

Study the balanced equation. 2Fe + 3H2O →→ Fe2O3 + 3H2(M Fe = 55.8 g/mol, M H2O = 18.0 g/mol, M Fe2O3 = 159.7 g/mol, M H2 = 2.0 g/mol) If 1.24 mol of water react, how many grams of iron(III) oxide (Fe2O3) would be produced?

66.0 g Fe2O3

3.13 g of sodium (Na) react with 7.17 g of chlorine (Cl2) to produce 10.3 g of sodium chloride (NaCl). What is the mass percent of chlorine in sodium chloride?

69.6% is chlorine.

Review the balanced equation and lab scenario. 2C10H11NO4 + 2H2O →→ C16H10N2O2 + 2C2H4O2 + 4H2O In this reaction, 1.38 g of indigo (C16H10N2O2) are produced. If the theoretical yield is 1.75 g of C16H10N2O2, what is the percent yield of indigo?

78.9%

How many particles are in 1.40 x 107 mol of aluminum (Al)? (HINT: Remember that there are 6.02 x 1023 particles in a mol of an element.)

8.43 ×× 1030 particles Al

What is the percent yield of copper (Cu) based on Group C's results?

86.5%

Through stoichiometric calculations, the theoretical yield of iron(III) oxide was calculated to be 12.3 g. However, when massed after the reaction, only 10.7 g of iron(III) oxide had been produced. What is the percent yield of iron(III) oxide?

87.0%

How does Avogadro's number relate to atomic mass?

Avogadro's number allows the conversion between atomic mass in amu and the mass of one mole in grams.

How does Avogadro's number relate to the number of moles?

Avogadro's number explains that one mole contains 6.02 x 1023 particles in any sample of a given compound or element. Therefore, when given the number of particles, scientists can calculate the number of moles.

During a laboratory experiment, 2.48 g of BaF2 react with 9.43 g NaNO3 to produce 1.19 x 100 g of NaF. BaF2 + 2NaNO3 →→ Ba(NO3)2 + 2NaF What is the limiting reactant?

BaF2

Examine the table of hydrogen (H) and oxygen (O) compounds. If Compound A is H2O, what are Compounds B and C likely to be?

Compound B: HO Compound C: H2O2

Examine the table of oxygen (O) and nitrogen (N) compounds. If Compound A is NO, what are Compounds B and C likely to be?

Compound B: NO2 Compound C: N2O2

Lesson 24

Conversions

Read the statement and refer to the unbalanced chemical equation. A sample of 6.49 g of fluorine (F2) reacts with 4.15 g of chlorine (Cl2) to produce 1.05 x 101 g of chlorine trifluoride (ClF3). F2 + Cl2 →→ ClF3 What is the limiting reactant? (HINT: Remember to balance the equation first, and then refer to the periodic table for the molar masses.)

F2

Lesson 28

Formulas

What is the importance of the mole concept in chemistry? Select all that apply.

It allows chemists to study and measure substances within the subatomic world. It allows chemists to change grams to the number of particles through the mole, even though particles cannot be seen.

Lesson 26

Limiting Reactants

Examine the chemical equation. 2Mg(s) + O2(g) →→ 2MgO(s) If 5 mol of magnesium (Mg) are combined with 5 mol of oxygen gas (O2) to produce magnesium oxide (MgO), which substance is the limiting reactant, and which is the excess reactant?

Mg is the limiting reactant; O2 is the excess reactant.

Lesson 25

Mole Ratios

Read the chemical equation. 2N2 + O2 →→ 2N2O If 0.49 mol of nitrogen reacts with 0.49 mol of oxygen, what is the limiting reactant?

N2

During a lab experiment, 30 mol of NH3 are combined with 30 mol of sulfuric acid (H2SO4). 2NH3 + H2SO4 →→ (NH4)2SO4 What is the limiting reactant?

NH3

What is true about proportions? Select all that apply.

Proportions have cross products that are equal. Proportions can be written as equal fractions.

Lesson 23

The Mole

How do moles relate to atomic mass?

The mass of a mole in grams is equal to atomic mass in amu.

How is the mole used by chemists?

The mole allows scientists to measure samples of substances that cannot be seen (by converting the amount of particles to grams).

How is it that the atomic mass of an element can be converted to the mass of one mole?

because the atomic mass in amu is equal to the mass of one mole in grams

What is the name of the compound CO?

carbon monoxide

Carbon and oxygen form two polyatomic ions: CO22− and CO32−. What is the name of CO22−?

carbonite

Which reactant will have a remaining amount when the reaction is complete, and which will be fully consumed first, completing the reaction?

excess reactant, limiting reactant

What is the name of the compound NO2?

nitrogen dioxide

Chlorine and oxygen form four polyatomic ions: ClO−, ClO2−, ClO3−, ClO4−. What is the name of ClO4−?

perchlorate

Is the following mathematical expression a proportion or a ratio? 2H2/1O2

ratio, because it shows a relationship between two compounds

What unit in chemistry allows chemists to study and measure substances that are too small to be seen or counted?

the mole

What is an excess reactant?

the reactant that is only partially used up in a chemical reaction and remains left over after the maximum amount of product is formed

What is a limiting reactant?

the reactant that will be fully consumed first, completing the reaction

How did scientists calculate the most exact value for the mole?

through x-ray diffraction of silicon atoms

When might it be important for an industrial company to know the theoretical yield of a chemical reaction? Select all that apply.

when the company wants to determine the amount of product they can create; when the company wants to determine the percent yield and identify if the process is cost-effective when the company wants to learn what the limiting reactant is; when the company wants to understand the amount of materials they will need for production

At standard temperature and pressure, how many L of fluorine gas (F2) are there in 3.01 mol of it?

xxx 1.34 ×× 10-1 L of F2

How many mol of NO are produced from a reaction if its mass is 2.05 g?

xxx 1.46 ×× 102 mol NO

How many mol of potassium (K) are present in cereal that claims to have 7.00 g of potassium per serving?

xxx 3.13 ×× 10-1 g K

What is the purpose for a company to determine percent yield of a product and not just the theoretical yield?

xxx The percent yield enables the calculation of the maximum amount of error that can be expected, which may help determine loss of profit, minimal amount of reactant to use, and the inefficiency of the system.

Is the following mathematical expression a proportion or a ratio? 3CO2/6O2 = 9CO2/18O2

xxx proportion, because it shows a relationship between two compounds