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Questions and Answers
What is the formula mass of baking soda (NaHCO3)?
What is the formula mass of baking soda (NaHCO3)?
- 84 g/mol (correct)
- 94 g/mol
- 104 g/mol
- 74 g/mol
What are cations?
What are cations?
- Atoms that have gained electrons
- Positively charged ions (correct)
- Negatively charged ions
- Neutrally charged atoms
To determine the formula mass of ammonium nitrate (NH4NO3), which of the following must be calculated?
To determine the formula mass of ammonium nitrate (NH4NO3), which of the following must be calculated?
- The total mass of nitrogen, hydrogen, and oxygen (correct)
- The mass of ammonium only
- Only hydrogen and oxygen mass combined
- The mass of only nitrogen and hydrogen
How are free radicals described in the context of chemical species?
How are free radicals described in the context of chemical species?
What typically happens to metal atoms in terms of charge?
What typically happens to metal atoms in terms of charge?
What is the primary role of potassium chlorate (KClO3) in a laboratory setting?
What is the primary role of potassium chlorate (KClO3) in a laboratory setting?
What characterizes an ionic compound?
What characterizes an ionic compound?
What is the main action that results in the formation of anions?
What is the main action that results in the formation of anions?
What is the molecular mass of glucose (C6H12O6)?
What is the molecular mass of glucose (C6H12O6)?
Which term is used specifically for molecular compounds?
Which term is used specifically for molecular compounds?
What is the formula mass of sodium chloride (NaCl)?
What is the formula mass of sodium chloride (NaCl)?
What is the molecular mass of naphthalene (C10H8)?
What is the molecular mass of naphthalene (C10H8)?
Which formula represents the simplest ratio of cations and anions in an ionic compound?
Which formula represents the simplest ratio of cations and anions in an ionic compound?
What is the relative atomic mass of hydrogen based on its mass as a percentage of a C-12 atom?
What is the relative atomic mass of hydrogen based on its mass as a percentage of a C-12 atom?
What is the empirical formula of glucose given the simplest ratio of C, H and O atoms is 1:2:1?
What is the empirical formula of glucose given the simplest ratio of C, H and O atoms is 1:2:1?
What is the formula mass of magnesium hydroxide (Mg(OH)2)?
What is the formula mass of magnesium hydroxide (Mg(OH)2)?
Which of the following elements has a relative atomic mass closest to 15.9994 amu?
Which of the following elements has a relative atomic mass closest to 15.9994 amu?
Which statement is true about ionic compounds?
Which statement is true about ionic compounds?
When calculating molecular mass, what does the term 'subscript' refer to?
When calculating molecular mass, what does the term 'subscript' refer to?
If the molecular formula of hydrogen peroxide is H2O2, what is its empirical formula?
If the molecular formula of hydrogen peroxide is H2O2, what is its empirical formula?
What does the molecular formula of a compound indicate compared to the empirical formula?
What does the molecular formula of a compound indicate compared to the empirical formula?
Which element has the highest relative atomic mass among the following options?
Which element has the highest relative atomic mass among the following options?
Which of the following formulas represents the relative atomic mass of Sodium?
Which of the following formulas represents the relative atomic mass of Sodium?
What is the simplest whole-number ratio of hydrogen to oxygen in water?
What is the simplest whole-number ratio of hydrogen to oxygen in water?
What was Archimedes tasked with determining regarding the crown?
What was Archimedes tasked with determining regarding the crown?
Which observation did Archimedes make while bathing that led to his discovery?
Which observation did Archimedes make while bathing that led to his discovery?
What principle did Archimedes use to determine the purity of the crown?
What principle did Archimedes use to determine the purity of the crown?
Which branch of chemistry deals with the substances that Archimedes was investigating?
Which branch of chemistry deals with the substances that Archimedes was investigating?
What does the term 'Eureka' signify in Archimedes' discovery?
What does the term 'Eureka' signify in Archimedes' discovery?
What physical sensation did Archimedes experience when submerged in water?
What physical sensation did Archimedes experience when submerged in water?
How did Archimedes plan to test the crown's purity?
How did Archimedes plan to test the crown's purity?
Which branch of chemistry focuses on the large-scale production of useful substances?
Which branch of chemistry focuses on the large-scale production of useful substances?
What is the mass of hydrogen peroxide (H2O2) that would contain 2.5 moles?
What is the mass of hydrogen peroxide (H2O2) that would contain 2.5 moles?
How many moles of H2O2 are there in a 30g sample?
How many moles of H2O2 are there in a 30g sample?
What is the number of moles in 12.5 grams of sodium chloride (NaCl)?
What is the number of moles in 12.5 grams of sodium chloride (NaCl)?
What is the mass of one mole of barium sulfate (BaSO4)?
What is the mass of one mole of barium sulfate (BaSO4)?
How many atoms are present in 1.25 moles of zinc (Zn)?
How many atoms are present in 1.25 moles of zinc (Zn)?
How many molecules are in 0.5 moles of methane (CH4)?
How many molecules are in 0.5 moles of methane (CH4)?
How many atoms are present in 0.2 moles of aluminum (Al)?
How many atoms are present in 0.2 moles of aluminum (Al)?
How many molecules are in 0.25 moles of sulfur dioxide (SO2)?
How many molecules are in 0.25 moles of sulfur dioxide (SO2)?
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Study Notes
Archimedes' Contribution to Density Measurement
- Tasked by the Greek emperor to determine the purity of a gold crown using carbonates, bicarbonates, and oxides.
- The principle of buoyancy discovered while bathing led to the concept of displaced liquid volume.
- Concluded that loss of weight when submerged in water equals the weight of the displaced liquid.
- Designed an experiment to weigh the crown against pure gold: if densities matched, the crown was pure; if not, it was impure.
- His famous exclamation "Eureka" signified his realization and discovery process.
Branches of Chemistry
- Inorganic Chemistry: Focuses on elements and compounds excluding organic compounds.
- Biochemistry: Studies physical and chemical changes in living organisms.
- Industrial Chemistry: Involves large-scale production of useful substances and methods using technology.
Atomic Mass and Relative Atomic Mass
- Mass of a C-12 atom is defined as 12 amu; hydrogen is 8.40% as massive as the C-12 atom.
- Relative atomic mass of hydrogen calculated: 1.008 amu.
- Relative atomic masses of key elements:
- Oxygen (O): 15.9994 amu
- Sodium (Na): 22.9898 amu
- Aluminum (Al): 26.9815 amu
- Iron (Fe): 55.847 amu
- Chlorine (Cl): 35.453 amu
- Nitrogen (N): 14.0067 amu
- Sulfur (S): 32.06 amu
Chemical Formulas
- Empirical Formula: Represents the simplest whole-number ratio of elements. Example: Hydrogen peroxide (H2O2) has an empirical formula of HO.
- Molecular Formula: Shows the actual number of atoms of each element in a molecule. Example: Glucose (C6H12O6).
- Molecular mass calculations:
- For glucose: C: 6(12.00) + H: 12(1.008) + O: 6(16.00) = 180.096 amu.
- For naphthalene (C10H8): 120 (C) + 8 (H) = 128 amu.
Formula Mass vs. Molecular Mass
- Molecular mass applies to molecular compounds; formula mass applies to ionic compounds.
- Example of ionic compound: Sodium Chloride (NaCl) has a formula mass of 58.5 amu.
- Milk of magnesia (Mg(OH)2) formula mass calculated: 24 (Mg) + 32 (O) + 2 (H) = 58 amu.
Ions and Chemicals
- Definition of ions: Charged species formed from atoms by adding or removing electrons.
- Cations: Positively charged (e.g., Na+), Anions: Negatively charged (e.g., Cl-).
- Ionic compounds consist of equal numbers of cations and anions to maintain neutrality.
Mole-Particles Calculations
- Understanding that one mole equals Avogadro's number (6.022 × 10²³):
- For Zn: 1.25 moles = 7.53 × 10²³ atoms.
- For Al: 0.2 moles = 1.2044 × 10²³ atoms.
- Mole calculations for molecules:
- Methane (CH4): 0.5 moles = 3.011 × 10²³ molecules.
- Sulfur dioxide (SO2): 0.25 moles = 1.505 × 10²³ molecules.
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