Chapter 3 Flashcards
How do you start to balance chemical equations?
Start with an element that is only in one reactant and product.
What do you change while balancing chemical equations?
Balance it by changing coefficients, Not subscripts.
What are combination reactions?
Two or more substances react to form one product.
What two substances would create a combination reaction?
A metal and a nonmetal.
What are decomposition reactions?
In a decomposition reaction, one substance breaks down into two or more substances.
What is an example of a decomposition reaction?
Heating a metal carbonate and it decomposing into carbon dioxide and a metal oxide.
What are combustion reactions?
Combustion reactions are rapid reactions that produce a flame.
What must combustion reactions involve as a reaction?
Combustion reactions most often involve oxygen in the air as a reactant.
What is formula weight?
A formula weight is the sum of the atomic weights for the atoms in a chemical formula.
What is molecular weight?
If the substance is a molecule, the formula weight is also called its molecular weight.
How do you find percentage composition?
% Element = [(number of atoms of the element)(atomic weight of the element) / FW of the substance] x 100
How do you convert grams to moles?
moles = mass (g) / molar mass (g/mol)
How do you convert moles to formula units?
Formula units = moles x Avogadro’s number (6.022 x 10^23)
How do you determine the empirical formula?
Convert mass% to grams, convert grams to moles, and calculate mole ratio.
What is the mole ratio?
The ratio between the amounts in moles of any two compounds involved in a balanced chemical reaction.
How could it be possible to turn percents to grams?
You assume the amount is 100 grams.
When calculating mole ratio, which number of moles do you divide by?
Calculate the mole ratio for each element by dividing by the smallest number of moles.
When you receive the mole ratio, what do you do with it?
It becomes the superscript.
How do you find molecular formulas from empirical formulas?
(compound’s molar mass / molar mass of the empirical formula) x each superscript in the empirical formula
What is stoichiometry?
How to compare two different materials, using the mole ratio from the balanced equation.
Where does the mole ratio come from?
The mole ratio comes from the coefficients in the balanced equation.
What are the steps of finding a formula’s stoichiometric relationship?
Find the moles of substance A from grams, use coefficients of the balanced equation to find moles of substance B, then find grams of substance B.
What is the limiting reactant?
The limiting reactant is the reactant present in the smallest stoichiometric amount.
What is theoretical yield?
The theoretical yield is the maximum amount of product that can be made, calculated through stoichiometry.
