Gr 10 Physical Sciences Ch 14: Composition
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Questions and Answers

What is the main purpose of understanding the composition of compounds in chemistry?

  • To determine the chemical reactivity of a substance
  • To determine the solubility of a substance
  • To determine the physical properties of a substance
  • To determine the ratio and number of atoms present in a compound (correct)

    • How many types of composition problems are commonly encountered in chemistry?

  • 2
  • 5
  • 4 (correct)
  • 3

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

  • Determine the molar mass of the compound (correct)
  • Divide the mass of each element by the atomic mass of the element
  • Convert the percentage of each element to grams
  • Calculate the mass of each element in one mole of the compound

    • What is the purpose of determining the empirical formula of a compound?

    <p>To determine the simplest whole-number ratio of the elements in a compound</p> Signup and view all the answers

    What is the purpose of multiplying the empirical formula by a whole number factor?

    <p>To determine the molecular formula</p> Signup and view all the answers

    What is the result of dividing the moles of each element by the smallest number of moles in determining the empirical formula?

    <p>The simplest whole-number ratio of the elements in a compound</p> Signup and view all the answers

    Which of the following is NOT a step in combustion analysis?

    <p>Measuring the pH of the solution</p> Signup and view all the answers

    What is the purpose of heating the hydrate in determining waters of crystallisation?

    <p>To remove the water of crystallisation</p> Signup and view all the answers

    What is the unit of measurement for the percentage by mass of each element in a compound?

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

    What is the purpose of combustion analysis in chemistry?

    <p>To determine the formula of a reactant from the products of a chemical reaction</p> Signup and view all the answers

    What is the result of dividing the moles of water by the moles of anhydrous compound?

    <p>Number of waters of crystallisation</p> Signup and view all the answers

    What is the result of dividing the mass of each element by the molar mass of the compound in calculating the percentage by mass of each element?

    <p>The percentage by mass of each element</p> Signup and view all the answers

    What is the name given to compounds that crystallize with water molecules incorporated into their solid structure?

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

    What is the purpose of combustion analysis?

    <p>To determine the empirical formula of a compound containing carbon, hydrogen, and oxygen</p> Signup and view all the answers

    What is the reason for multiplying the empirical formula by a whole number factor?

    <p>To determine the molecular formula</p> Signup and view all the answers

    What is measured in the first step of combustion analysis?

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

    What is calculated from the mass of water lost in determining waters of crystallisation?

    <p>The moles of water</p> Signup and view all the answers

    What is the purpose of calculating the moles of carbon and hydrogen in combustion analysis?

    <p>To determine the empirical formula of the compound</p> Signup and view all the answers

    What is determined by dividing the moles of water by the moles of anhydrous compound?

    <p>The number of waters of crystallisation</p> Signup and view all the answers

    What is the product of combustion analysis that is used to determine the empirical formula?

    <p>CO₂ and H₂O, and sometimes oxygen</p> Signup and view all the answers

    What is the primary information provided by the empirical formula of a compound?

    <p>The simplest whole-number ratio of the elements in the compound</p> Signup and view all the answers

    Which of the following steps is NOT involved in calculating the percentage by mass of each element in a compound?

    <p>Divide the moles of each element by the smallest number of moles</p> Signup and view all the answers

    What is the first step in determining the empirical formula from percentage composition?

    <p>Convert the percentage of each element to grams</p> Signup and view all the answers

    What is the purpose of calculating the percentage by mass of each element in a compound?

    <p>To determine the amount of each element present in the compound</p> Signup and view all the answers

    In determining the empirical formula, what is the purpose of dividing the moles of each element by the smallest number of moles?

    <p>To get the simplest whole-number ratio of the elements</p> Signup and view all the answers

    What is the result of converting the percentage of each element to grams in determining the empirical formula?

    <p>The moles of each element</p> Signup and view all the answers

    What type of analysis is used to determine the formula of a reactant from the products of a chemical reaction?

    <p>Combustion analysis</p> Signup and view all the answers

    What is the purpose of calculating the mass of each element in one mole of the compound?

    <p>To determine the percentage by mass of each element</p> Signup and view all the answers

    What is the purpose of combustion analysis?

    <p>To determine the empirical formula of a compound containing carbon, hydrogen, and oxygen</p> Signup and view all the answers

    What is the ratio of the moles of water to the moles of anhydrous compound in determining waters of crystallisation?

    <p>The number of moles of water per mole of anhydrous compound</p> Signup and view all the answers

    Why is the empirical formula multiplied by a whole number factor?

    <p>To match the compound's known molar mass</p> Signup and view all the answers

    What is the product of combustion analysis that is used to determine the empirical formula?

    <p>The moles of carbon, hydrogen, and oxygen</p> Signup and view all the answers

    What is the purpose of measuring the mass of the hydrate before and after heating?

    <p>To determine the number of waters of crystallisation</p> Signup and view all the answers

    What is the result of combustion analysis?

    <p>The empirical formula of the compound containing carbon, hydrogen, and oxygen</p> Signup and view all the answers

    What is the primary purpose of calculating the percentage by mass of each element in a compound?

    <p>To provide detailed information about the ratio and number of atoms present in a compound</p> Signup and view all the answers

    What is the first step in determining the empirical formula from percentage composition?

    <p>Convert the percentage of each element to grams</p> Signup and view all the answers

    What is the result of dividing the mass of each element by the molar mass of the compound in calculating the percentage by mass?

    <p>The percentage by mass of the element</p> Signup and view all the answers

    What is the purpose of determining the empirical formula of a compound?

    <p>To provide detailed information about the ratio and number of atoms present in a compound</p> Signup and view all the answers

    What is the product of combustion analysis that is used to determine the empirical formula?

    <p>The moles of carbon and hydrogen</p> Signup and view all the answers

    What is the primary information provided by the molecular formula of a compound?

    <p>The exact number of atoms present in the compound</p> Signup and view all the answers

    What is the purpose of calculating the mass of each element in one mole of the compound?

    <p>To determine the percentage by mass of each element</p> Signup and view all the answers

    What type of analysis is used to determine the formula of a reactant from the products of a chemical reaction?

    <p>Combustion analysis</p> Signup and view all the answers

    What is the primary difference between the molecular formula and the empirical formula of a compound?

    <p>The molecular formula represents the actual number of atoms in a compound, while the empirical formula represents the simplest whole-number ratio.</p> Signup and view all the answers

    What is the purpose of dividing the moles of each element by the smallest number of moles in determining the empirical formula?

    <p>To determine the mole ratios of each element.</p> Signup and view all the answers

    What is the result of converting the percentage of each element to grams in determining the empirical formula?

    <p>The mass of each element in one mole of the compound.</p> Signup and view all the answers

    What is the purpose of calculating the mass of each element in one mole of the compound?

    <p>To determine the percentage composition of each element.</p> Signup and view all the answers

    What is the result of determining the empirical formula of a compound?

    <p>The simplest whole-number ratio of the elements in the compound.</p> Signup and view all the answers

    What is the purpose of combustion analysis in chemistry?

    <p>To determine the molecular formula of a compound from the products of a chemical reaction.</p> Signup and view all the answers

    What is the result of determining the percentage by mass of each element in a compound?

    <p>The ratio of the mass of each element to the total mass of the compound.</p> Signup and view all the answers

    What is the primary purpose of calculating the moles of each element in determining the empirical formula?

    <p>To determine the mole ratios of each element.</p> Signup and view all the answers

    What is the significance of the empirical formula's molar mass differing from the compound's known molar mass?

    <p>It allows for the determination of the molecular formula.</p> Signup and view all the answers

    During combustion analysis, what is the role of the moles of carbon and hydrogen?

    <p>They are used to determine the empirical formula of the compound.</p> Signup and view all the answers

    What is the purpose of measuring the mass of the hydrate before and after heating in determining waters of crystallisation?

    <p>To determine the moles of water lost during heating.</p> Signup and view all the answers

    What is the relationship between the empirical formula and the molecular formula?

    <p>The molecular formula is a multiple of the empirical formula.</p> Signup and view all the answers

    What is the significance of the remaining mass in combustion analysis?

    <p>It is used to calculate the moles of oxygen present.</p> Signup and view all the answers

    What is the purpose of multiplying the empirical formula by a whole number factor?

    <p>To determine the molecular formula of the compound.</p> Signup and view all the answers

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