Question

Study Guide Chapter 3

What is average mass? What is average atomic mass? What is the atomic mass?

What is the mole? If you have a mole of cheese, how many pieces of cheese do you have?

What is the Avogdro’s number? What is this number used for?

How do we use the mole in chemical reactions?

Students must be able to calculate the mass of given numbers of atoms of an element. For example, calculate the mass of 10 atoms of carbon. See example 3.2.

Students must be able to calculate the moles of atoms. See example 3.3.

Students must be able to calculate number of atoms. See example 3.3.

Students must be able to calculate number of moles and mass.

What is molar mass? Students must be able to calculate the molar masses for a given compound. For example, calculate the molar mass of C₆H₁₂O₆. See examples 3.6 and 3.7 and 3.8.

Discuss, in as many details as you can, the conceptual problem solving approach.

What is percent composition? What is the percent mass composition of C₆H₁₂O₆. See example 3.9.

What is the formula of a compound? How can we determine the formula of a compound? How do we determine the empirical formula of a compound? What type of data do we need to have to determine the empirical formula for a compound? What type of data do we need to have to determine the molecular formula of a compound? How do we determine the molecular formula from the empirical formula?

A compound that contains only C, H and O is 48.64% C and 8.16% H. What is the empirical formula for this compound? See examples 3. 10 – 3.12.

What is a chemical reaction? What is a chemical equation? Describe a chemical equation in detail. Students must learn how to do read a chemical equation.

Why are we required to balance chemical equations? How do we balance chemical equations? See examples 3.13 – 3.14.

What is stoichiometric calculations? When do we perform such calculations? See examples 3.15 – 3.16.

What is a limiting reagent? How do we calculate the limiting reagent? What type of data do we need to calculate the limiting reagent?

What is theoretical yield? What is actual (experimental) yield? What is percent yield? What does percent yield mean?

Answer 1

Average Mass is the sum of masses of all the elements and Average atomic Mass is the mass of all the elements of its isotopes multiplied by its natural abundance.

Atomic Mass is the mass of an atom expressed in atomic mass units . It is approximately equal to sum no of protons and neutrons.

Mole is the amount of chemical substance that contains representative particles that is atoms , ions , molecules. 1 mole of cheese would have Avagadro Number of pieces.

Avagadro constant ( NA )is the number of Particles ; atoms , molecules in one mole of substance . The Value of NA : 6.023E + 23.

Has many applications Used to calculate moles of substance present .

To calculate Moles of compound we divide Mass of element by its Molar Mass.

The molar mass can be calculated by adding the standard atomic mass of the constituent elements.

Percentage Composition is the mass of each element present.

Percentage Compostion of glucose is 40% Carbon , 6.7 % Hydrogen and 53.3% Oxygen.

Mass of Glucose is 180

Mass of 6 carbon is 72

Divide 72/180 = .40 * 100 = 40%

Assume you have 100g of masses. Convert it into mole . Divide moles by the smallest mole value and ypu will get the % composition.

Emperical formula is C2H4O

Chemical Reaction is a rearrangement of a atom or a molecule distinct from change in physical reaction.

Chemical equation in which number of moles of reactants on left hand side is equal to number of moles of product on product side.

Stochiometric Calculations in which we have to deal our problems by converting into moles.

Use the mole ratio to find the desired substance.

Limiting Reagent is The chemical substance that is totally consumed when the reaction is complete

Reaction in which one substance is present in less amount.

Theoritical Yield which is the Literature value .

And percentage yield is the calculated upon theoritical yield.