Gr 10 Physical Science: Ch 14 Sum Quantitative aspects of chemical change

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Questions and Answers

What is defined as the amount of product actually obtained from a reaction?

  • Theoretical Yield
  • Actual Yield (correct)
  • Percentage Yield
  • Reversible Yield

How is percentage yield calculated?

  • Total Reactants divided by Theoretical Yield, multiplied by 100
  • Theoretical Yield divided by Actual Yield, multiplied by 100
  • Actual Yield divided by Theoretical Yield, multiplied by 100 (correct)
  • Actual Yield divided by Loss of Product

If the theoretical yield is 72 g of water and the actual yield is 60 g, what is the percentage yield?

  • 66.67%
  • 72.00%
  • 83.33% (correct)
  • 90.00%

Which of the following is NOT a factor that can lead to a difference between actual yield and theoretical yield?

<p>Accurate measurements (D)</p> Signup and view all the answers

Why is stoichiometry important in chemical processes?

<p>It is essential for predicting reaction outcomes and optimizing reactant quantities. (D)</p> Signup and view all the answers

Which of the following fields relies on stoichiometry?

<p>Environmental Science (D)</p> Signup and view all the answers

What is the definition of a mole?

<p>The SI unit for the amount of substance containing $6.022 \times 10^{23}$ particles (A)</p> Signup and view all the answers

How many particles does one mole contain?

<p>$6.022 \times 10^{23}$ (A)</p> Signup and view all the answers

What is the molar mass of carbon?

<p>12 g·mol$^{-1}$ (D)</p> Signup and view all the answers

In the reaction between iron and sulfur, how many atoms of sulfur react with one atom of iron?

<p>One atom (C)</p> Signup and view all the answers

What does the molar mass represent for an element?

<p>The mass of one mole of the element in grams (B)</p> Signup and view all the answers

How many grams of copper corresponds to one mole?

<p>63.5 g (D)</p> Signup and view all the answers

Which statement best describes Avogadro's number?

<p>It is the number of particles in one mole of a substance. (B)</p> Signup and view all the answers

What is the relationship between molar mass and atomic mass for an element?

<p>Molar mass is numerically equal to the atomic mass expressed in grams per mole. (B)</p> Signup and view all the answers

What is the correct relationship between mass, molar mass, and the number of moles?

<p>$n = rac{m}{M}$ (A)</p> Signup and view all the answers

How do you calculate the molar mass of a compound like nitric acid (HNO₃)?

<p>Add up the molar masses of hydrogen, nitrogen, and oxygen atoms. (C)</p> Signup and view all the answers

In the equation N₂ + 3H₂ → 2NH₃, how many moles of hydrogen are needed for each mole of ammonia produced?

<p>3 moles (A)</p> Signup and view all the answers

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

<p>22.99 g·mol⁻¹ + 35.45 g·mol⁻¹ (A)</p> Signup and view all the answers

What does the mole ratio in a balanced chemical equation indicate?

<p>The proportion of reactants that react together. (A)</p> Signup and view all the answers

What can you determine by knowing the composition of a compound?

<p>The empirical or molecular formula. (A)</p> Signup and view all the answers

When calculating the percentage by mass of elements in a compound, which of the following steps is necessary?

<p>Divide the mass of each element by the total mass of the compound. (D)</p> Signup and view all the answers

Which statement about formula mass is incorrect?

<p>It applies only to covalent compounds. (A)</p> Signup and view all the answers

In a combustion analysis, what is primarily determined from the products?

<p>The formula of the reactants. (B)</p> Signup and view all the answers

Which of the following is NOT a type of composition problem in chemistry?

<p>Determining the number of lone pairs (D)</p> Signup and view all the answers

What is the theoretical yield of water produced from the complete reaction of 4 moles of hydrogen with 2 moles of oxygen?

<p>72 g (C)</p> Signup and view all the answers

How do you calculate concentration if 0.3 moles of KCl are dissolved in 2 dm³ of water?

<p>0.15 mol·dm⁻³ (D)</p> Signup and view all the answers

What volume of oxygen gas can be obtained from 2 moles of hydrogen gas at S.T.P.?

<p>11.2 dm³ (C)</p> Signup and view all the answers

What is the mass of 3 moles of NaCl?

<p>174 g (D)</p> Signup and view all the answers

What is the relationship between moles, mass, and molar mass?

<p>Mass = Moles × Molar Mass (D)</p> Signup and view all the answers

How do you find the number of moles from a given volume of gas at S.T.P.?

<p>Divide the volume by 22.4 dm³/mole (A)</p> Signup and view all the answers

What might cause the actual yield to be less than the theoretical yield in a chemical reaction?

<p>All of the above (D)</p> Signup and view all the answers

What process would you use to convert grams of a reactant to moles?

<p>Divide the mass by the molar mass (B)</p> Signup and view all the answers

Which statement correctly describes stoichiometry?

<p>It involves calculating the ratios of reactants and products. (A)</p> Signup and view all the answers

Which of the following is an essential step in calculating theoretical yield?

<p>Converting reactants to moles (D)</p> Signup and view all the answers

What is the first step in calculating the percentage by mass of an element in a compound?

<p>Determine the molar mass of the compound. (C)</p> Signup and view all the answers

Which of the following steps is NOT part of determining the empirical formula when given percentage composition?

<p>Divide by the molar mass of the entire compound. (B)</p> Signup and view all the answers

What does combustion analysis primarily measure to determine the empirical formula of a compound?

<p>The masses of CO₂ and H₂O produced. (D)</p> Signup and view all the answers

How can the number of waters of crystallisation in a hydrate be determined?

<p>By calculating the mass of the hydrate before and after heating. (A)</p> Signup and view all the answers

What is the molar volume of a gas at standard temperature and pressure?

<p>22.4 dm³ (C)</p> Signup and view all the answers

What is the correct formula for calculating concentration?

<p>C = rac{n}{V} (C)</p> Signup and view all the answers

In the combustion analysis, how are moles of oxygen determined if it is present in the compound?

<p>By using the remaining mass after carbon and hydrogen calculations. (D)</p> Signup and view all the answers

What role does the empirical formula play in relation to the molecular formula?

<p>It represents the simplest whole-number ratio of elements. (A)</p> Signup and view all the answers

Why is the concept of molar volume significant in gas reactions?

<p>It aids in calculating the amount of reactants and products. (D)</p> Signup and view all the answers

Which process is involved in determining the number of moles of water lost from a hydrate?

<p>Calculating the mass difference before and after. (C)</p> Signup and view all the answers

Study Notes

Atomic Mass and the Mole

  • Chemical equations detail reactants and products but not the amounts involved.
  • One mole (mol) corresponds to ( 6.022 \times 10^{23} ) particles, known as Avogadro's number.
  • Molar mass (M) of an element is the mass of one mole, measured in grams per mole (g·mol(^{-1})).
  • Example: Carbon's molar mass is 12 g·mol(^{-1}), and 63.5 grams of copper equals one mole of copper atoms.
  • The relationship between mass (m), molar mass (M), and moles (n) is expressed as ( n = \frac{m}{M} ).

Compounds and Molar Mass

  • Molar mass can be calculated by summing the molar masses of all atoms in a compound.
  • A balanced chemical equation indicates the mole ratios of reactants to products.
  • Example reaction: ( \text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3 ) indicates one mole of nitrogen reacts with three moles of hydrogen to produce two moles of ammonia.
  • The formula mass aggregates the atomic masses in a formula unit for compounds like NaCl and HNO(_3).

Composition of Compounds

  • Composition helps determine empirical or molecular formulas, detailing the ratio and number of atoms.
  • Types of composition problems include:
    • Calculating percentage by mass of each element.
    • Determining formulas from percentage composition.
    • Analyzing combustion reaction products for empirical formula determination.
    • Calculating moles of crystallization waters in hydrates.

Amount of Substance

  • The mole quantifies the amount of substance, allowing for predictions on reactant combinations and product formations.
  • Molar volume for gases at standard temperature and pressure (S.T.P.) is 22.4 dm³ per mole.
  • Concentration, denoted as ( C = \frac{n}{V} ), measures solute amount per volume of solution.

Stoichiometric Calculations

  • Stoichiometry links moles, mass, volume, and concentration, predicting product amounts from reactant quantities.
  • The theoretical yield indicates the maximum product quantity from a reaction based on stoichiometry.
  • Calculations for theoretical yield follow these steps:
    • Balance the chemical equation.
    • Convert reactant quantities to moles.
    • Use mole ratios to determine product moles.
    • Convert product moles to mass.
  • Actual yield is the measured amount of product; percentage yield reflects reaction efficiency: ( \text{Percentage Yield} = \left( \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \right) \times 100 ).

Importance of Stoichiometry

  • Stoichiometry is vital in various fields for predicting reaction outcomes and optimizing processes.
  • It aids in scaling reactions for industrial use and minimizing waste through efficient reactant quantity determination.

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