Unit 2 - Stoichiometry

• Define: combustion reaction


  a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light
• What are the products when a hydrocarbon is burned?

  carbon dioxide and water
• Classify the reaction below:MgO(s)+ CO2-> MgCO3(s)

  Combination (composition, synthesis), 1 product
• How many particles are in a mole?

  6.022e23
• What is the formula for percentage yield?

  actual yield/theoretical yield x 100

  
• What is a hydrocarbon?

  a compound made of hydrogen and carbon atoms
• Write a generic equation representing a decomposition reaction.

  one reactant produces two or more products

  
• Write a generic equation representing a single replacement reaction.

  a single element replaces an element found in a compound

  
• Write a generic equation representing a double replacement reaction.

  The atoms/ions in two compounds essentially switch places.

  
• Write a generic equation representing a combination/ synthesis reaction.

  two or more reactants make one product

  
• List the three simple hydrocarbons you should know.

  methane, ethane, propane

  
• Define the law of conservation of mass.

  Mass cannot be created or destroyed during a chemical reaction.
• What is the equation used to calculate average mass?

  Avg mass = (relative abundance)(mass of isotope)+(relative abundance)(mass of isotope)+.....
• Write the balanced equation for the combustion of carbon monoxide.

  The combustion of carbon monoxide is:

  
• Balance the following chemical reaction:CH3NH2 + O2---> CO2 + H2O + N2


  answer: 4 CH3NH2 + 9 O2 ---> 4 CO2 + 10 H2O + 2 N2
• Define: molar mass


  sum of the average atomic weights of each element in the formula
• Define: limiting reactants (reagent)

  the reactant that is consumed first in a reaction
• Define: molecular formula


  chemical formula that gives the total number of moles of each element in each molecule of a substance
• What are the common oxides of carbon, hydrogen, and sulfur?

  carbon dioxide, water, and sulfur dioxide

  
• Define: empirical formula


  chemical formula showing the simplest ratio of elements in a compound rather than the total number of moles in the molecule
• Define: actual yield


  the amount of product actually obtained during an experiment
• Define: theoretical yield


  the amount of product predicted by stoichiometry
• What are the products when a carbonate decomposes?

  carbon dioxide and a metal oxide
• What are the products when a chlorate decomposes?

  oxygen and a metal chloride
• What are the products when a hydroxide decomposes?

  water and a metal oxide
• What is produced when a sulfate decomposes?

  sulfates do not decompose (hydrate lab)
• Define: atomic mass scale

  a relative scale, now based on C-12, and measured in amu
• Define: mole ratio


  a conversion factor between compounds in a chemical reaction, that is derived from the coefficients of the compounds in a balanced equation
• Define: hydrate


  a compound in which there is a specific ratio of water to ionic compound
• Define: anhydrate (or anhydrous)


  an ionic compound without water; the ionic compound left when a hydrate is heated
• What is Avogadro's Number?

  6.022e23 (atoms, molecules, particles, etc.)
• List the five generic reactions.

  combination, decomposition, single-replacement, double-replacement, and combustion
• Describe mass spectrometry.

  a process where molecules are broken into fragments, which are characteristic of the molecule; the fragments collide with a detector and a spectrum is generated relaying information regarding isotopes and abundance
• True / False: It is possible to use periodic table to predict reactions because members of a family behave similarly.


  true
• Describe the percentage method used to find the molecular formula.

  1st - take % and apply to the whole compound's molar mass; 2nd - divide the product by the element's molar masses.
• Describe the empirical formula method used to find the molecular formula.

  1st - assume percentages are grams; 2nd - divide it by the element's molar mass; 3rd - divide by smallest number; if the ratio is _.1 round down to nearest whole number; if the ratio is _.9 round up to nearest whole number; if the ratio is between _.2 and _.8 find the multiple to make the ratio a whole number. Once the empirical formula has been found, divide the mass of the molecular formula by the mass of the empirical formula to find the multiple. Multiply the empirical formula by the multiple to find the molecular formula.
• Describe the method used to find percent composition.

  Find the type and number of each element in a compound. Multiply the elements by their molar masses. Find the total mass by adding up the individual masses. To find the percentage, divide the total mass of each element by the mass of the compound and then multiply by 100.
• Define: AMU


  atomic mass unit; mass of 1 proton/ neutron; 1/12 the mass of carbon-12 atom
• Describe the easy method for determining mass of excess reactant when only one product is made.

  total mass of reactants - mass of products made
• What law does stoichiometry depend on?

  Law of Conservation of Mass