Chemistry Lecture 5: Reactions and Ions
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Questions and Answers

What is the name of the ion that is formed when a hydrogen atom loses an electron?

Hydrogen ion

What is the name of the ion that is formed when a copper atom loses one electron?

Copper(I) or cuprous ion

What is the name of the ion formed when an ammonium molecule gains one electron?

Ammonium ion

What is the name of the ion that is formed when a cobalt atom loses two electrons?

<p>Cobalt(II) or cobaltous ion</p> Signup and view all the answers

What is the name of the ion that is formed when an iron atom loses two electrons?

<p>Iron(II) or ferrous ion</p> Signup and view all the answers

What is the name of the ion that is formed when a manganese atom loses two electrons?

<p>Manganese(II) or manganous ion</p> Signup and view all the answers

What is the name of the ion that is formed when a mercury atom loses one electron?

<p>Mercury(I) or mercurous ion</p> Signup and view all the answers

What is the name of the ion that is formed when a nickel atom loses two electrons?

<p>Nickel(II) or nickelous ion</p> Signup and view all the answers

What is the name of the ion that is formed when an aluminum atom loses three electrons?

<p>Aluminum ion</p> Signup and view all the answers

What is the name of the ion that is formed when a chromium atom loses three electrons?

<p>Chromium(III) or chromic ion</p> Signup and view all the answers

What is the name of the ion that is formed when a hydrogen atom gains one electron?

<p>Hydride ion</p> Signup and view all the answers

What is the name of the ion that is formed when a fluorine atom gains one electron?

<p>Fluoride ion</p> Signup and view all the answers

What is the name of the ion that is formed when a cyanide molecule gains one electron?

<p>Cyanide ion</p> Signup and view all the answers

What is the name of the ion that is formed when an oxygen atom gains two electrons?

<p>Oxide ion</p> Signup and view all the answers

What is the name of the ion that is formed when a carbon atom and three oxygen atoms gain two electrons?

<p>Carbonate ion</p> Signup and view all the answers

What is the name of the ion that is formed when a chromium atom and four oxygen atoms gain two electrons?

<p>Chromate ion</p> Signup and view all the answers

What is the name of the ion that is formed when two chromium atoms and seven oxygen atoms gain two electrons?

<p>Dichromate ion</p> Signup and view all the answers

What is the name of the ion that is formed when a sulfur atom and four oxygen atoms gain two electrons?

<p>Sulfate ion</p> Signup and view all the answers

What is the name of the ion that is formed when a phosphorus atom and four oxygen atoms gain three electrons?

<p>Phosphate ion</p> Signup and view all the answers

What is the name of the ion that is formed when a nitrogen atom gains three electrons?

<p>Nitride ion</p> Signup and view all the answers

The molecular weight of water is 18.0 amu.

<p>True</p> Signup and view all the answers

What is the molecular weight of ethane, C2H6?

<p>30.070 amu</p> Signup and view all the answers

What is the mass percentage of hydrogen in water?

<p>11.189%</p> Signup and view all the answers

Ionic compounds use molecular weights.

<p>False</p> Signup and view all the answers

What is the formula weight of calcium chloride (CaCl2)?

<p>110.99 amu</p> Signup and view all the answers

A mole is the measure of material containing 6.02214 × 10^{23} particles.

<p>True</p> Signup and view all the answers

One mole of carbon-12 atoms contains 6.02214 × 10^{23} atoms.

<p>True</p> Signup and view all the answers

What is the molar mass of oxygen?

<p>16.00 g/mol</p> Signup and view all the answers

What is the molar mass of oxygen gas (O2)?

<p>32.00 g/mol</p> Signup and view all the answers

What is the molar mass of sodium chloride (NaCl)?

<p>58.44 g/mol</p> Signup and view all the answers

The empirical formula is the simplest whole-number ratio of the atoms in a compound.

<p>True</p> Signup and view all the answers

The molecular formula is the simplest whole-number ratio of the atoms in a compound.

<p>False</p> Signup and view all the answers

What is the empirical formula for a compound that contains 61.31% carbon, 5.14% hydrogen, 10.21% nitrogen, and 23.33% oxygen?

<p>C7H7NO2</p> Signup and view all the answers

What is the empirical formula for a compound that contains 68.4% chromium and 31.6% oxygen?

<p>Cr2O3</p> Signup and view all the answers

What is the empirical formula for a compound that contains 60.3% magnesium and 39.7% oxygen?

<p>MgO</p> Signup and view all the answers

What is the molecular formula for a compound that has an empirical formula of C4H8O and a molar mass of 216 g/mol?

<p>C12H24O3</p> Signup and view all the answers

Combustion analysis is a technique used to analyze organic compounds.

<p>True</p> Signup and view all the answers

Avogadro's number has been defined as a ratio of 12 grams to 12 amu.

<p>True</p> Signup and view all the answers

Study Notes

Lecture 5 - Reading Assignments

  • Current reading: Brown Chapter 3.2-3.5 (mass fractions, moles)
  • Upcoming reading: Brown Chapter 3.6-3.7 (reaction yield, limiting reagents)

Lecture 5 - Homework

  • Homework 2 is due tonight.

Common Cations and Anions

  • Tables with common cations and anions (formula, charge, and name) are presented.
  • Focus on learning common ions, as they are used most frequently.

Balanced Equations

  • Example question: Balance the equation C4H9OH(l) + O2(g) → CO2(g) + H2O(g)
  • Additional example: Ca3(PO4)2(s) + 3H2SO4(aq) → 3CaSO4(s) + 2H3PO4(aq)

Three Basic Types of Reactions

  • Types of reactions include: Combination, decomposition, and combustion
  • Combination reactions involve two or more substances forming one product.

Combination Reactions

  • Examples of combination reactions:
  • 2 Mg(s) + O2(g) → 2 MgO(s)
  • N2(g) + 3 H2(g) → 2 NH3(g)
  • C3H6(g) + Br2(l) → C3H6Br2(l)

Decomposition Reactions

  • In a decomposition reaction, one substance breaks down into two or more substances.
  • Examples of decomposition reactions:
  • CaCO3(s) → CaO(s) + CO2(g)
  • 2 KCIO3(s) → 2 KCl(s) + O2(g)
  • 2 NaN3(s) → 2 Na(s) + 3 N2(g)

Combustion Reactions

  • Combustion reactions generally involve a substance reacting with oxygen to produce a flame.
  • Examples include:
  • CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
  • C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g)

Molecular Weight, Formula Weight, & Percent Composition

  • Molecular weight: Sum of atomic weights of atoms in a molecule.
  • Formula weight: Sum of atomic weights of atoms in an ionic compound.
  • Percent composition: Percentage of a substance's mass coming from a particular component

Example of a percentage calculation

  • Calculate the percentage composition of H,C, and O in oxalic acid (H2C2O4)

Ionic Compounds and Formulas

  • Ionic compounds are composed of ions in a three-dimensional arrangement rather than discrete molecules.
  • Ionic compounds are represented by empirical formulas, which represent the simplest ratio of ions.

Formula Weight (FW)

  • Formula weight is the sum of the atomic weights of the atoms in an ionic compound formula.
  • Example calculation for Calcium Chloride (CaCl2): 1 calcium (40.08 amu) + 2 chlorine (35.453 amu) = 110.99 amu

The Mole (3.4)

  • A mole is a unit of measurement representing 6.02214 x 10^23 particles (atoms or molecules).
  • The mole is used to relate the number of particles to the mass of a substance.

Avogadro's Number (NA)

  • Avogadro's number (NA) is 6.02214 x 1023.
  • This is the number of atoms or molecules in a mole.

Molar Mass

  • The mass of one mole of a substance in grams. It is numerically equal to the formula weight (in amu).

Mole Relationships

  • 1 mole of a substance contains Avogadro's number of particles.
  • The number of moles of an element in a compound depends on the number and type of atoms in the molecule.

Stoichiometric Calculations and the Mole Bridge

  • Relationship between moles and other quantities such as grams, molarity, and liters.
  • Shows possible conversions between various units relating to moles.

Determining a Chemical Formula from Experimental Data (3.5)

  • Empirical formula: Simplest whole-number ratio of atoms in a compound.
  • Percent composition used for determining empirical formula; assume a 100-gram sample.

Determining Empirical Formulas

  • Method for finding the empirical formula; steps to follow.
  • Convert percentages to grams (assuming 100g sample)
  • Convert grams to moles using molar mass.
  • Determine the mole ratio by dividing by the smallest number.
  • Multiply the values to reach the whole number ratio for subscripts in the formula

Example of determining empirical formulas

  • Use percentages to determine the empirical formula for para-aminobenzoic acid (PABA).

Determining Molecular Formulas

  • Relationship between molecular formula, an appropriate multiple of the empirical formula, and molar mass

Example of determining molecular formulas

  • Combustion analysis example calculating the molecular formula from data

Combustion Analysis

  • Technique for determining the composition of a substance by burning it and finding the mass of products.

Re-defining the Kilogram

  • Avogadro's number is used to relate 12 grams of an element to 12 amu

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CHEM 141 Lecture 5 PDF

Description

This quiz covers key concepts from Chemistry Lecture 5, including common cations and anions, balanced equations, and the three basic types of chemical reactions: combination, decomposition, and combustion. Pay attention to the examples provided as they are crucial for understanding these concepts.

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