Chapter9First7pages

Testing Advertising Claims about Antacids

• Objective: Assess a company's claim that its antacid tablet neutralizes ten times more stomach acid than a competitor's product.

• Approach:

  • Conduct an experiment to compare the acid-neutralizing capacity of both products.

  • Use a controlled environment to measure pH changes when equivalent amounts of each antacid are added to a standardized amount of acid.

  • Analyze the data to determine if the claim holds under scientific scrutiny.

Calculating Acid Requirements for Methanol Production

• Scenario: Working for a chemical company to produce 6.0 kg of methanol (CH3OH).

• Determination Steps:

  • Use the balanced equation for the production of methanol:

    • Unbalanced Reaction: CO(g) + H2(g) → CH3OH(l)

    • Balanced Reaction: CO(g) + 2H2(g) → CH3OH(l)

  • Calculate moles of methanol to be produced:

    • Molar mass of CH3OH = 32.04 g/mol.

    • Moles of methanol = 6000 g / 32.04 g/mol ≈ 187.5 moles.

  • Use mole ratios from the balanced reaction to find the required amounts of CO and H2:

    • Ratio: 1 mol CO to 2 mol H2.

    • Moles of CO needed = 187.5 moles (methanol) * (1 mol CO / 1 mol CH3OH) = 187.5 moles CO.

    • Moles of H2 needed = 187.5 moles (methanol) * (2 mol H2 / 1 mol CH3OH) = 375 moles H2.

  • Convert moles to grams for ordering:

    • Molar mass of CO = 28.01 g/mol; mass of CO = 187.5 moles * 28.01 g/mol ≈ 5250 g CO.

    • Molar mass of H2 = 2.02 g/mol; mass of H2 = 375 moles * 2.02 g/mol ≈ 757.5 g H2.

Understanding Chemical Equations and Their Ratios

Importance of Balanced Equations

• Chemical equations represent the identities and quantities of reactants and products.

• Coefficients in a balanced equation indicate the relative number of molecules or moles involved in the reaction.

Example: Making Deli Sandwiches

• Analogy: Making sandwiches to understand mole ratios:

  • Equation: 2 pieces of bread + 3 slices of meat + 1 slice of cheese → 1 sandwich.

  • For 50 sandwiches: Multiply coefficients by 50 resulting in 100 pieces of bread, 150 slices of meat, and 50 slices of cheese.

Example: Reaction for Methanol Production

• Reactants and Products: CO(g) + 2H2(g) → CH3OH(l)

• Balance and interpret the equation:

  • Reactants needed for 1 mole of methanol include 1 mole of CO and 2 moles of H2.

Mole Concept

• Mole Definition: 6.022 x 10^23 units (Avogadro's number).

• Example Balancing:

  • For the reaction: CO(g) + 2H2(g) → CH3OH(l)

  • Alternative representation in terms of moles:

    • 1 mol CO + 2 mol H2 → 1 mol CH3OH.

Mole-Mole Relationships

Practical Application: Decomposition of Water

• Chemical Reaction:

  • 2H2O(l) → 2H2(g) + O2(g)

• Calculation Example:

  • Given 4 mol of water:

    • From balanced equation: 2 mol H2O → 2 mol H2 + 1 mol O2.

  • Therefore, for 4 mol H2O:

    • Yields 4 mol H2 and 2 mol O2.

Using Mole Ratios for Reactants

• Example Problem: Finding O2 needed for 4.30 mol of propane reaction.

  • Balanced Equation: C3H8 + 5O2 → 3CO2 + 4H2O

  • Mole Ratio: 1 mol C3H8 requires 5 mol O2.

  • Calculation:

    • 4.30 mol C3H8 × (5 mol O2 / 1 mol C3H8) = 21.5 mol O2 needed.