UNIT 4: Quantifying Reactions Flashcards
what should the total mass before and after a reaction be?
the total mass before and after the reaction should be the same
what is one mole equal to?
6.022x10^23
what’s a hydrate
an ionic compound that has absorbed water. A certain number of water molecules can co-crystallize with the salt.
Ex:Na2SO4 ∙ 10H2O (sodium sulfate decahydrate)
MgCl2 ∙ 6H2O (magnesium chloride hexahydrate)
what does anhydrous mean
without water
whats the steps to calculating a hydrate
First, calculate the number of moles of anhydrous salt. Next calculate the number of moles of water. Last, calculate the ratio of the two in order to determine the formula of the hydrate
what does structural formulas tell you
exact # of atoms in a molecule
what does a chemical formulas tell you about a molecule
is a compact representation of a chemical. For covalent compounds, this is also called the compound’s molecular formula.
what does empirical formulas tell you about a molecule
reduces the subscripts in the molecular formula to the smallest whole numbers.
how do you convert mass percentages to formulas
1) Assume you have 100 g
2) Convert the masses of each element
to moles
3) Divide each number of moles by the
smallest number of moles to get the ratios
whats the law of conservation of mass
Matter cannot be created or destroyed.
In a chemical reaction, the EXACT number and type of atoms NEVER changes. This is why we balance reactions.
whats a combustion reaction
A combustion reaction is any reaction involving a fuel and an oxidant and usually accompanied by a flame.
Combustion reactions are exothermic
(they give off heat).
Combustion reactions require energy to get started (activation energy).
what are the products of combustion dependent on, in order to make water?
The products of combustion reactions depend on the reactants. If the fuel contains hydrogen, water must be a product of combustion. Also, the water will ALWAYS be in the form of steam.
what makes the products of carbon dioxide in a combustion reaction
If the fuel contains carbon, carbon dioxide will be a product of combustion if there is enough oxygen. If there is enough oxygen, the reaction is called “complete combustion.”
whats an incomplete combustion
If there is NOT enough oxygen, a mixture of carbon dioxide, carbon monoxide, and carbon soot will be produced.
Carbon monoxide is extremely toxic and is the #1 cause of poisoning deaths in the U.S.
Carbon monoxide is also flammable.
whats a combustion reaction
A combination reaction is any reaction in which ONE product is made from the combination of two (or more) reactants. The reactants are often pure elements. Combination reactions are also called synthesis reactions.
whats a decomposition reaction
A decomposition reaction is any reaction in which one reactant decomposes, or breaks down, into two or more products. A decomposition reaction is the reverse of a combination reaction.
whats an acid base reaction
In an acid base reaction, there is a transfer of one or more hydrogen ion(s) from the acid to the base. The hydrogen ion is H+. Often water is a product. Sometimes a gas, like CO2 is given off.
single replacement reaction
In a single replacement reaction (aka single displacement reaction), there are two reactants and two products. One of the reactants is in its elemental form, and one of the products is in its elemental form. In the single replacement reaction, one element (or polyatomic ion) trades partners.
whats a double replacement reaction
This reaction is called a double replacement
reaction because both reactants are changing
partners. The insoluble CaCO3 is a precipitate
what do all double replacement reactions have
1) 2 reactants and 2 products (all ionic compounds)
2) Both reactants switch partners
3) At least one product is insoluble, indicated by (s)
whats a theoretical yield
The amount of product you should get if the reaction works perfectly.
when would you not get a theoretical yield
The reaction does not work “perfectly” Some reactant does not react Some product gets blown away Some product gets stuck to the container Equipment errors Human errors Etc.
actual yield
what you measure in the lab. It is how much you actually got in real life.
percent yield of reaction
The Percent Yield of a reaction is a measure of how well it worked.
how do you calculate the percent yield
actual yield/ theoretical yield x 100%
whats a limiting reagent
- The Limiting Reagent of a reaction is the reactant that limits the amount of product formed.
