Chemistry Applied Science

• Why is the first ionisation energy of silicon greater than that of germanium?

  Silicon has a higher nuclear charge than germanium
• What does the Aufbau principle state?

  Electrons fill the lowest energy orbitals first
• What is the formula for methane?

  CH₄
• What is the structure of methane?

  Tetrahedral with bond angles of 109°
• What happens to aluminium in air?

  It forms a protective oxide layer
• What is the balanced equation for aluminium reacting with air?

  4Al + 3O₂ → 2Al₂O₃
• What is Avogadro's constant?02 x 10²³ particles
• How do you calculate the number of moles in 136 g of potassium?

  Number of moles = mass / A_r
• What is the formula for calculating the number of moles (N)?

  N = C x V (in dm³)
• How is relative atomic mass calculated


  isotopic mass x relative abundance + isotopic mass x relative abundance / 100.
• how do you calculate the number of moles in a given mass


  moles = mass / relative atomic mass.
• how do you calculate concentration of solutions


  concentration = mass / volume.
• In ionisation energy when the nuclear charge increases across the period what happens to the electrons?


  the electrons are more attracted to the nucleus, which means that ionisation energy increases across the period.
• when does ionisation energy decrease?


  ionisation energy decreases if the electron configuration is in a different sub shell as it increases the distance from the nucleus preventing attraction.

  
  

  This makes the electron easier to extract reducing ionisation energy.
• what is electron affinity?


  the energy change that occurs when an electron is added to an atom
• what are the trends of electron affinity in the periodic table?


  electron affinity increases upwards and across periods because of the nuclear charge increase.
• what is nuclear charge?


  number of protons in the nucleus
• What happens to atomic radius across a period from left to right?

  Atomic radius decreases due to increased nuclear charge
• How do you determine the outer shell of electrons in an element.


  draw atomic structure and figure out the electrons in its outer most shell, or look at the group number to determine the outer shell of electrons in an element.
• What are intermolecular forces?


  forces of attraction between molecules.
• What is the trend in ionic radii of cations and anions across a period?

  Cations decrease, anions increase in size
• What is the atomic radius?

  The distance from the nucleus to the outermost electron
• How much CaCl₂ is produced from 50 g of CaCO₃?

  55 g
• What are the trends in ionic radius for cations and anions across a period?

  • Cations decrease in size across a period.
  • Anions increase in size across a period.
• What does isoelectronic mean?

  Having the same numbers of electrons
• Which element is the most electronegative?

  Fluorine
• What trends are observed in melting and boiling points of elements in group 7?

  • Melting and boiling points increase down the group.
  • Forces of attraction get stronger.
• What happens when an element melts?

  Energy overcomes attractive forces between atoms
• What happens when an element boils?

  Most attractive forces between atoms are broken
• What properties allow metals to be malleable and ductile?

  • Atoms can roll over each other.
  • Metallic bonding allows movement without breaking.
• How do delocalised electrons contribute to metallic properties?

  They carry electric charge and absorb heat energy
• What is the role of silicon dioxide and carbon monoxide in industrial chemistry?

  • Silicon dioxide is used in glass making.
  • Carbon monoxide is used in iron extraction.
• How does burning carbon in air lead to carbon monoxide formation?

  Incomplete combustion produces carbon monoxide
• Write the balanced equation for the reaction between silicon and oxygen.

  Si + O₂ → SiO₂
• What is a basic solution?

  • A solution with a pH above 7.
• What are allotropes?

  • Different physical forms of an element.
  • Example: graphite and diamond for carbon.
• What is an amphoteric substance?

  • A substance that can act as both an acid and a base.
• What is the reactivity series?

  • A list of metals ordered by reactivity.
  • Higher metals are more reactive.
• What happens to a metal higher in the reactivity series?


  It has a higher tendency to lose electrons
• What occurs when a more reactive metal displaces a less reactive metal?

  The more reactive metal replaces the less reactive one