CHEM 99D: Introduction to Chemistry

CHEM 99D: Introduction to Chemistry

Basic Chemistry Concepts

  • Introduction to Key Elements:

    • Rutherfordium (Rf) - Atomic number 104

    • Dubnium (Db) - Atomic number 105

    • Seaborgium (Sg) - Atomic number 106

    • Technetium (Tc) - Atomic number 43

    • Rhenium (Re) - Atomic number 75

    • Bohrium (Bh) - Atomic number 107

    • Mass of Different Elements

Reaction Examples

  • Sodium Azide Reaction:

    • Chemical Reaction: 2 ext{NaN}3(s) ightarrow 2 ext{Na}(s) + 3 ext{N}2(g)

    • Airbags: This reaction is used to rapidly inflate airbags by releasing nitrogen gas (N2).

    • Calculation: If we start with 6.00 g of sodium azide (NaN3), calculate the grams of nitrogen gas (N2) produced.

  • Photosynthesis Equation:

    • Overall Reaction: 6 ext{CO}2 + 6 ext{H}2 ext{O}
      ightarrow ext{C}6 ext{H}{12} ext{O}6 + 6 ext{O}2

    • Calculation: Amount of glucose ($ ext{C}6 ext{H}{12} ext{O}6$) produced from 4.40 g of carbon dioxide ($ ext{CO}2$).

  • Phosphorus and Oxygen Reaction:

    • Reaction: ext{P} + 5 ext{O}2 ightarrow 2 ext{P}2 ext{O}_5

    • Objective: If we require 45.0 grams of $ ext{P}2 ext{O}5$, calculate grams of oxygen needed in excess phosphorus.

  • Xenon Tetrafluoride Reaction:

    • Reaction: ext{XeF}4 + 2 ext{H}2 ext{O}
      ightarrow ext{Xe} + 4 ext{HF} + ext{O}_2

    • Calculation: Determine the mass of xenon tetrafluoride ($ ext{XeF}_4$) necessary to react completely with 1.000 g of water.

Worked Example on Titanium Tetrachloride Preparation

  • Reaction: ext{TiO}2 (s) + 4 ext{C} (s) + 6 ext{Cl}2 (g)
    ightarrow 3 ext{TiCl}4 (l) + 2 ext{CO}2 (g) + 2 ext{CO} (g)

  • Parameters:

    • Amounts reacted: 2.3 grams of TiO2, 0.45 grams of carbon (C), and 4.3 grams of chlorine gas.

    • Density of TiCl4: 1.73 g/mL

  • Calculation: Find the yield of TiCl4 in mL based on the given quantities of reactants.

Yield Calculations

  • Definitions of Yield:

    • Theoretical Yield: The maximum product based on the limiting reactant.

    • Actual Yield: The amount of product that is actually formed. Influenced by incomplete reactions and lab techniques.

    • Percent Yield Formula: ext{Percent Yield} = rac{ ext{actual yield}}{ ext{theoretical yield}} imes 100

    • Example:

      • Theoretical yield: 22 g of $ ext{H}3 ext{PO}3$

      • Actual yield: 18 g of $ ext{H}3 ext{PO}3$

      • ext{Percent Yield} = rac{18 g}{22 g} imes 100 = 81.82 ext{ %}

  • Percent Excess:

    • Formula: ext{Percent Excess} = rac{ ext{amount leftover}}{ ext{amount used up}} imes 100

    • Calculation example: From 0.7 mol of water, 0.41 mol used, ext{Percent Excess} = rac{0.7 - 0.41}{0.41} imes 100 = 171 ext{%}

Chemical Reaction Problem Examples

  • Lead Compounds Reaction:

    • Reaction: ext{PbO}2 + ext{Pb} + 2 ext{H}2 ext{SO}4 ightarrow 2 ext{PbSO}4 + 2 ext{H}_2O

    • Calculation: Given 1.45 g of Pb, 1.93 g of PbO2, and 100 mL of 0.15 M H2SO4, find the grams of PbSO4 produced and percent yield if 1.7 g of PbSO4 is formed.

  • Hydrocarbon Combustion:

    • Given: Combine 43.0 g of propane ($ ext{C}3 ext{H}8$) with 54.0 g of oxygen, find grams of carbon dioxide ($ ext{CO}_2$) produced and starting materials remaining.

  • Additional Reaction Calculations:

    • Assess reactions related to specific masses given various reactants, such as generating products from reactions involving silicon, magnesium, lead compounds, and more.

Calculating Grams Precipitated

  • Mixing Criteria:

    • To calculate precipitate of lead(II) iodide ($ ext{PbI}2$) formed by mixing 25.0 mL of 0.150 M potassium iodide ($ ext{KI}$) with 15.0 mL of 0.175 M lead(II) nitrate ($ ext{Pb(NO}3 ext{)}_2$).

Practical Safety Measures in Chemistry

  • Mustard Gas Reaction:

    • Chemical Reaction: (HO-CH2CH2)2S + ext{PCl}3 ightarrow (Cl-CH2CH2)2S + ext{P(OH)}3

    • Context: Challenge regarding labeling all chemicals and its importance for safety in laboratory environments.

    • Calculation: How many liters and molecules of mustard gas can be formed from a specific volume of reactants with known densities:

    • Thiodiglycol: density of 1.22 g/cm3

    • Phosphorus trichloride: density 1.597 g/cm3