Mistakes flashcards (chemistry)

• Gases with the slowest rate of diffusion?


  heavier gases diffuse slowly whereas lighter gases diffuse faster.
• element which has aqueous ions which form a white precipitate when added to aqueous silver ions

  Chlorine
• forms a blue hydroxide which dissolves in aqueous ammonia

  copper
• Element which is added to molten iron to remove impurities in the steel making process?

  oxygen
• in terms of particles why does rate of reaction decreases as time increases (mentioning concentration)

  As time increases concentration of particles decreases and have fewer Collisions
• one molecule of urea breaks down to form one molecule of ammonia and another molecule, what is the formula of the other molecule?

  HCNO
• two non toxic gases formed by incomplete combustion of fuel where a catalytic converter removes nitrogen monoxide by a gas via incomplete combustion of fuel, name the gas and two non toxic gases formed

  gas : carbon monoxide

  two non toxic gases : carbon dioxide and nitrogen
• metal that can replace zinc and increase reading on voltmeter

  carbon
• metal that can replace iron and increase reading on voltmeter

  copper
• ion half eq for reaction occurring when zinc electrode dissolves 


  $Zn ---> Zn^2+$$2e^-$
• three substances manufactured by passing electricity through brine (concentrated aqueous sodium chloride)

  1. hydrogen
  2. Chlorine
  3. sodium hydroxide
• a substance formed when molten sodium chloride is used instead of concentrated aqueous sodium chloride

  sodium
• type of chemical reaction which forms short-chain alkanes and alkenes from long chain alkanes

  cracking
• define water of crystallization

  water molecules present in hydrated crystals
• type of chemical reaction between : CaO + SiO2 ---> CaSiO3

  acid-base reaction
• define activation energy 


  minimum energy that colliding particles must have in order to react
• one way in which activation energy can be changed

  add a catalyst
• Avagadro's constant 


  6.02x10^23
• physical properties of aluminum that make it suitable for use in overhead electrical cables

  low density

  good conductor of electricity
• why is aluminum unreactive ?

  because it reacts readily with oxygen to form a protective oxide layer which is unreactive
• calcium and water make calcium hydroxide, what other substance reacting with water makes calcium hydroxide ?

  calcium oxide
• test for presence of calcium ions in a sample of limewater ?

  test: aqueous sodium hydroxide

  observation: white precipitate
• gas produced in the test for nitrate ions

  Ammonia
• when aqueous ammonia is added to aqueous iron (II) sulfate a green precipitate is formed, what is the green ppt? why does It turn red brown at the surface ? what happens if excess aq ammonia is added to the green ppt

  green ppt = iron (II) hydroxide

  it turns red-brown because it reacts with oxygen and is oxidized

  and no change is seen when excess aq ammonia is added to green ppt.
• greenhouse effect 


  when greenhouse gases, like carbon dioxide and methane absorb heat reflected off of the ground from the sun and this absorbed heat is re-emitted in to all direction reducing thermal energy lost to space and increases temperature of the earth causing global warming and climate change
• one condition required during esterification

  acid catalyst; for ethanol and ethanoic acid they will react in the presence of sulfuric acid
• what is a functional group

  atoms or group of atoms that give molecules their chemical properties
• what is a mixture

  two or more substances that are not chemically combined
• what is oxidation number 


  it is the charge on an atom, ion or molecule
• Rules for oxidation numbers

  1. if an atom or ion is neutral oxidation state is = 0 (eg Cl2 has O. number of 0)
  2. the charge on an ion is the same as its oxidation number
  3. Sum of oxidation number in a compound is = 0
  4. sum of oxidation number In an ion is equal to charge on the ion (for example NO2^-1 has the charge -1 so all oxidation number will add up to give you -1)
• identifying redox reactions

  1. Acidified aqueous potassium manganate (KMnO4) > is an oxidizing agent; it is used to test for presence of reducing agents. If reducing agent is present the color changes for PURPLE TO COLORLESS.
  2. Aqueous potassium iodide is a reducing agent; it is used to test for presence of oxidizing agents. if oxidizing agent is present color changes from colorless to red-brown.
• in the making of stainless steal name one other element other than carbon that is mixed with iron during this process...

  nickel
• describe bonding in a metallic element

  metallic bonding, where positive ions are surrounded by sea of delocalized electrons, the strong forces of attraction between positive and negative ions makes up the bond
• ionic bonding

  bonding between metals and non metals

  metals lose their outer shell electrons and non metals gain those electrons.

  the positive and negative ions are held together by strong forces of attraction between opposite charges and the force of attraction is the ionic bond
• covalent bonding

  bonding between non metals

  they have weak intermolecular forces and no free moving ions