Module 2 chemistry

• What is an isotope?

  Atoms with the same protons, different neutrons
• How is atomic structure represented by nuclear symbols?

  Using mass number and atomic number
• How can you deduce the atomic structure of an atom or ion?

  By analyzing protons, neutrons, and electrons
• What are the three subatomic particles in an atom?

  Proton, Neutron, Electron
• How many protons are in an atom of Lithium?

  3
• What does the relative atomic mass indicate?

  Total number of protons and neutrons
• How does an oxygen atom differ from an oxide ion?

  An oxide ion has two more electrons
• Why is the relative atomic mass often not a whole number?

  It averages all isotopes with different masses
• What is the atomic number?

  Number of protons in an atom
• What is the mass number?

  Total number of protons and neutrons
• How does the number of electrons in a neutral atom compare to protons?

  They are equal in a neutral atom
• How does the number of electrons change in ions?

  It varies depending on the charge of the ion
• How many protons and electrons does a magnesium ion (Mg²⁺) have?

  12 protons and 10 electrons
• What are the differences in subatomic particles between isotopes of Carbon?

  • a) C¹²: 6 protons, 6 neutrons, 6 electrons
  • b) C¹³: 6 protons, 7 neutrons, 6 electrons
  • c) C¹⁴: 6 protons, 8 neutrons, 6 electrons
• How do the isotopes of Iron differ and what do they have in common?

  • Different: Vary in number of neutrons
  • Similar: Same number of protons and electrons
• What are the subatomic particles in the following atoms and ions?

  • N: 7 protons, 7 neutrons, 7 electrons
  • K⁺: 19 protons, 20 neutrons, 18 electrons
  • Ag: 47 protons, 62 neutrons, 47 electrons
  • S^2-: 16 protons, 18 neutrons, 18 electrons
  • Pb: 82 protons, 125 neutrons, 82 electrons
  • Cr³⁺: 24 protons, 29 neutrons, 21 electrons
• What is the difference between Li and Li?

  Li⁷ has one more neutron
• How does O differ from O^2-?

  O^2- has two more electrons
• What is the difference between K⁺ and Ca²⁺?

  Ca²⁺ has one more proton
• What is Avogadro's number?

  6.02 x 10$^{23}$
• What does Avogadro's number represent?

  Number of particles in one mole
• What is a mole?

  A measurement of amount of substance
• How many particles are in one mole of any substance?

  6.02 x 10$^{23}$ particles
• What types of particles can be counted in moles?

  Atoms, ions, or molecules
• How is molar mass related to Mr?

  Molar mass equals the relative atomic mass
• How do you calculate the number of moles from mass and Mr?

  Moles = Mass ÷ Mr
• What is the Mr of Al₂O₃?

  102
• How many moles are in 5.1g of Al₂O₃?

  0.05
• How do you calculate the number of moles in 7g of MgCl₂?

  Moles = 7 ÷ 95.3
• How many particles are in 7g of MgCl₂?

  0.07345226 x 6.02 x 10$^{23}$
• How many chloride ions are in 7g of MgCl₂?

  8.84 x 10$^{22}$ chloride ions
• What is the relationship between moles and particles?

  • One mole contains 6.02 x 10$^{23}$ particles
  • Applies to atoms, ions, and molecules
• How do you find the molar mass of a compound?

  1. Identify the elements in the compound
  2. Find the atomic mass of each element
  3. Multiply by the number of atoms of each element
  4. Sum the total for all elements
• What are the steps to calculate moles from mass and molar mass?

  1. Measure the mass of the substance
  2. Determine the molar mass (Mr)
  3. Use the formula: Moles = Mass ÷ Mr
• What is the concentration of a solution?

  It is moles or grams per 1 dm³.
• How are concentration, moles, and volume linked?

  Concentration equals moles divided by volume.
• If 0.2 moles of calcium chloride are dissolved in 400 cm³ of water, what is the concentration?

  0.5 mol/dm³
• How do you calculate the moles of sodium hydroxide needed for a 2 mol/dm³ solution in 50 cm³ of water?

  0.10 moles
• What mass of sodium hydroxide is needed for 0.10 moles with a molar mass of 40 g/mol?

  4 g
• How do you calculate the mass of sodium carbonate for a 0.1 mol/dm³ solution?

  10.6 g