Stoichiometry and Mole Ratios

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Questions and Answers

What is the role of the stoichiometric factor in the calculations for the reactions occurring simultaneously?

To calculate the total volume of gas produced

To convert grams of reactants to moles of products (correct)

To balance the chemical equations

To determine the limiting reactant

From the example calculations, how is the amount of H2 produced from Al calculated?

By summing the weights of Al and Mg

By multiplying the mass of Al by its molar mass

By directly using the mass percentage of H2 in the alloy

By applying the mole ratio from the balanced equation (correct)

In the given reactions, what is the balanced equation for the production of H2 from magnesium?

Mg(s) + HCl(aq) → MgCl2(aq) + 2 H2(g)

Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g) (correct)

Mg(s) + 2 HCl(aq) → MgCl2(aq) + 2 H2(g)

2 Mg(s) + 2 HCl(aq) → 2 MgCl2(aq) + H2(g)

What mass of hydrogen gas is produced from 0.710 g of the magnesium-aluminum alloy sample?

0.0734 g H2 Signup and view all the answers

What is the molar mass of aluminum used in the stoichiometric calculations?

26.982 g/mol Signup and view all the answers

Which factor is used to convert from gas volume to moles in gas stoichiometry?

PV=nRT Signup and view all the answers

When calculating the mass of H2 produced from the magnesium reaction, which molar mass is used?

2.016 g/mol Signup and view all the answers

What is the total percentage composition of aluminum in the alloy described?

70.0% Signup and view all the answers

What is the molar ratio of CO2 produced to C6H14O4 consumed in the combustion reaction?

12:2 Signup and view all the answers

In the conversion pathway approach, what is the first step when calculating the mass of CO2 formed from triethylene glycol?

Convert grams of C6H14O4 to moles Signup and view all the answers

What is the balanced chemical equation for the combustion of triethylene glycol?

2 C6H14O4 + 15 O2 → 12 CO2 + 14 H2O Signup and view all the answers

When using stoichiometric calculations, what is the purpose of identifying the limiting reagent?

To find out how much product can be formed Signup and view all the answers

What is the molecular weight of triethylene glycol, C6H14O4, used in the calculations?

150.173 g/mol Signup and view all the answers

If you start with 4.16 g of C6H14O4, which step must be performed first to find the mass of CO2 produced?

Determine the moles of C6H14O4 used Signup and view all the answers

What is the mass of CO2 produced when burning 2.72 mol of triethylene glycol?

16.36 g CO2 Signup and view all the answers

How much O2 is consumed for the complete combustion of 6.86 g of C6H14O4?

15.5 g Signup and view all the answers

What does the stoichiometric coefficient of a substance in a balanced chemical equation represent?

The number of moles of that substance Signup and view all the answers

What is the mole ratio of O2 to H2O in the reaction 2H2 + O2 ⟶ 2H2O?

1:2 Signup and view all the answers

When conducting stoichiometric calculations, why is it important to use a balanced chemical equation?

To accurately relate the amounts of reactants and products Signup and view all the answers

In stoichiometry, what does the term 'conversion pathway' typically refer to?

The steps taken to convert from known reactants to unknown products Signup and view all the answers

What constant represents the number of particles in one mole of a substance?

Avogadro's number Signup and view all the answers

How would you calculate the mass of H2O produced from 5 moles of H2 in the reaction 2H2 + O2 ⟶ 2H2O?

Use the mole ratio to find moles of H2O and then convert to mass Signup and view all the answers

Study Notes

Stoichiometry

Stoichiometry measures the elements in a chemical reaction, relating the amounts of substances in a reaction
Stoichiometric factor (or mole ratio): Relates the amounts of any two substances involved in a chemical reaction, on a mole basis

Stoichiometric Factor Example

Every 2 moles of H2 consumed, produces 2 moles of H2O
Every 1 mole of O2 consumed, produces 2 moles of H2O
Every 1 mole of O2 consumed, consumes 2 moles of H2

Example: Relating the numbers of moles of reactant & product

Combustion of 2.72 mol of triethylene glycol, C6H14O4, in excess O2 produces 16.3 mol CO2
Balanced chemical equation: 2 C6H14O4 + 15 O2 → 12 CO2 + 14 H2O
The mole ratio of C6H14O4 to CO2 is 2:12
From this ratio, we can calculate the moles of CO2 produced

Example: Relating the mass of a reactant & product

The combustion of 4.16 g of C6H14O4 in excess O2 produces 7.31 g CO2
The calculation involves converting grams of C6H14O4 to moles of C6H14O4, then moles of C6H14O4 to moles of CO2, and finally moles of CO2 to grams of CO2

Example: Relating the masses of two reactants to each other

The combustion of 6.86 g of C6H14O4 in excess O2 consumes 226 g of C

Example: Calculating the quantity of a substance produced by reactions occurring simultaneously

A Mg-Al alloy with 70.0% Al and 30.0% Mg by mass produces 0.0734 g of H2 when reacted with excess HCl
The reaction involves two simultaneous reactions: Al + HCl and Mg + HCl
The total amount of H2 produced is the sum of the amounts produced by each reaction
To calculate the amount of H2, you need to consider the mass of Al and Mg in the alloy, convert them to moles, use the mole ratios from the balanced equations, and finally convert the moles of H2 to grams

Gas Stoichiometry

Volume is a factor in stoichiometry for gases
Ideal gas law: PV = nRT
The volume of 1 mole of an ideal gas at 0°C (273.15 K) and 1 atm is 22.4 L (molar volume)

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Description

Explore the principles of stoichiometry, including the calculations of reactants and products in chemical reactions. This quiz covers examples such as the combustion of triethylene glycol and its resulting carbon dioxide production. Test your understanding of stoichiometric factors and mole ratios.