Chemistry 151 Chapter 3 Flashcards

Questions and Answers

What is the mass, in grams, of 1.67 mol of Xenon (Xe)?

219.254

Calculate the amount (mol) of Rubidium (Rb) in 2.21 g.

0.026

A sample contains 7.68×10^24 atoms of Chlorine (Cl). Calculate the amount of Cl in mol.

What is the molecular weight of Ca3(PO4)2?

310.17 Signup and view all the answers

What is the mass of a sample of ethanol, C2H6O, containing 0.397 mol?

18.3 Signup and view all the answers

How many moles of lead(II) chromate (PbCrO4) are in 57.1 g?

0.177 Signup and view all the answers

The formula for converting mass (g) to moles using molecular weight is quantity (g) x 1 (mol)/ _______.

molar mass(g) Signup and view all the answers

To calculate the number of molecules in a given mass, use the molar mass to convert from mass in grams to ______.

moles Signup and view all the answers

How many molecules are there in a 4.70 g sample of HCl?

7.75 x 10^22 Signup and view all the answers

What is Avogadro's number?

6.022 x 10^23 Signup and view all the answers

Define a mole (mol).

the amount of a substance that contains 6.02 x 10^23 representative particles of that substance Signup and view all the answers

One mole of any element has a mass in grams equal to its ______.

atomic weight Signup and view all the answers

How many grams are in 1 mol of carbon atoms?

12.011 Signup and view all the answers

What is molecular mass?

the mass in AMU of one molecular compound Signup and view all the answers

Define the atomic weight of an element.

weighted average mass of the elements' naturally occurring isotopes Signup and view all the answers

Define the molecular weight of a substance.

weighted average mass of substances molecules Signup and view all the answers

Define formula weight.

sum of the atomic weights of all atoms in a formula unit of any compound, molecular or ionic Signup and view all the answers

How many grams of HCl are in 0.536 mol?

19.6 Signup and view all the answers

How many moles of ethylene gas, C2H4, are in 15.0 g?

0.536 Signup and view all the answers

What is a chemical equation?

A description of the identities & proportions of reactants & products Signup and view all the answers

Define reactants in a chemical reaction.

substances consumed during a chemical reaction Signup and view all the answers

Define products in a chemical reaction.

substances formed Signup and view all the answers

What does a chemical formula or chemical equation represent?

The formula CO can be used to represent one molecule of carbon monoxide, but it can also be used to represent a vast number of carbon monoxide molecules. Signup and view all the answers

Why are chemical equations always balanced?

Law of mass conservation Signup and view all the answers

Balance the chemical equation: CH4 + O2 --> CO2 + H2O.

CH4 + 2O2 -> CO2 + 2H2O Signup and view all the answers

What is a coefficient in a chemical equation?

A number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction. Signup and view all the answers

An aqueous solution is indicated by ______.

(aq) Signup and view all the answers

A gas is indicated by ______.

(g) Signup and view all the answers

A liquid is indicated by ______.

(l) Signup and view all the answers

A solid is indicated by ______.

(s) Signup and view all the answers

What is a combination reaction?

A + B --> C Signup and view all the answers

What is a decomposition reaction?

C --> A + B Signup and view all the answers

What are combustion reactions?

Rapid reactions that produce a flame; most often include oxygen. Signup and view all the answers

What is stoichiometry?

the mole ratios among the reactants & products in a chemical reaction Signup and view all the answers

Study Notes

Moles and Mass Calculations

Xenon (Xe) has a molar mass of 131.29 g/mol; 1.67 mol of Xe weighs approximately 219.25 g.
Rubidium (Rb) has a molar mass of 85.47 g/mol; 2.21 g of Rb equals 0.026 mol.
Chlorine (Cl) sample with 7.68×10²⁴ atoms can be converted to moles by dividing the number of atoms by Avogadro's number (6.022×10²³).
Lead(II) chromate (PbCrO₄) has a molar mass of 323 g/mol, and 57.1 g corresponds to approximately 0.177 mol.
Ethanol (C₂H₆O) has a molecular weight of 46.08 g/mol; a sample of 0.397 mol has a mass of 18.3 g.

Molecular Weight and Conversion

Molecular weight of Ca₃(PO₄)₂ is calculated as 310.17 amu, factoring in contributions from calcium, phosphorus, and oxygen.
To convert mass to moles, apply the formula: mass (g) x 1 mol/molar mass (g) = amount in mol.
For molecule quantification: first convert grams to moles, then use Avogadro's number to find the total number of molecules.

Avogadro's Number and Moles

Avogadro's number: 6.022 x 10²³ represents the number of atoms or molecules in one mole of a substance.
One mole of any element has a mass in grams equal to its atomic weight; for example, 1 mol of carbon atoms equals 12.011 g.

Chemical Fundamentals

Molecular mass is defined as the mass of one molecular compound in atomic mass units (amu).
Atomic weight refers to the weighted average of an element's naturally occurring isotopes.
Formula weight is the sum of the atomic weights in a formula unit, applicable to both molecular and ionic compounds.

Chemical Equations and Reactions

A chemical equation describes reactants and products' identities and proportions in a reaction.
Reactants are substances consumed during a chemical process, while products are formed post-reaction.
Chemical formulas can represent a single molecule or numerous identical molecules.

Principles of Balancing Reactions

Chemical equations must be balanced based on the law of mass conservation, ensuring equal numbers and kinds of atoms on both sides of the reaction.
Example: Balancing CH₄ + O₂ produces CO₂ + H₂O can be represented as CH₄ + 2O₂ → CO₂ + 2H₂O.

Types of Reactions

Different reaction types:
- Combination reactions: A + B → C
- Decomposition reactions: C → A + B
- Combustion reactions: Involving rapid reactions that produce flames, usually with oxygen.

Miscellaneous Definitions

Aqueous solution: Denoted as (aq).
Gas: Denoted as (g).
Liquid: Denoted as (l).
Solid: Denoted as (s).
Stoichiometry relates to mole ratios among reactants and products in chemical reactions.

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Test your knowledge with these flashcards from Chemistry 151 Chapter 3. Focus on understanding the conversion of moles to grams using the molar mass of elements. Perfect for students looking to reinforce their grasp of fundamental chemistry concepts.