Review/Miscellaneous
How many Carbon atoms are in the following compound: Fe2(CO3)3
What is...
3 Carbon atoms
This represents the number 6.02 x 1023. It is also known as Avogadro's (Avocado's Number).
What is...
a mole.
For the molecule, N2O5, how many moles of Oxygen atoms are there in 1 mole of N2O5?
Answer:
5 moles
Convert 11.2 Liters of CO2 gas to Moles of CO2 gas.
What is...
0.5 Liters of CO2 gas
Given the following molecular formula, what is the empirical formula for the following:
C6H14
What is...
C3H7
Avogadro's number is used with what units?
(moles, liters, molecules, atoms, grams)
What is...
Molecules AND atoms
The conditions meant by STP for gases (Standard Temperature and Pressure)
What is...
0o Celsius and 1 atm
What is the formula mass for AgNO3 (silver nitrate)?
What is...
169.88 amu (atomic mass units)
What is the mass of 0.87 moles of NH3?
What is...
14.82 grams
***remember that when the problem is asking for "mass" you need to use the Molar Mass to convert.
The empirical formula of a compound is CH2O and the Molar Mass is 180. What is the molecular formula?
What is...
C6H12O6
**if you are given the empirical formula and the molar mass, you can only find the empirical formula.
Why do we use Avogadro's number?
What is...
Because atoms are very very very very very small.
It makes the numbers easier to work with.
This refers to the relative amounts of the elements in a compound.
What is...
the percent composition
What is the Molar Mass of lead (IV) nitrate [Pb(NO3)4]?
What is...
455.24 g/mol
***remember that units for Molar Mass are g/mol. Units for formula mass are amu.
What is the percent composition of all the elements in glucose (C6H12O6)?
What is...
39.7% Carbon; 53.6% Oxygen; and 6.8% Hydrogen
What is the empirical formula of a compound which consists of 89.14% Au and 10.80% of O?
What is...
Au2O3
***If you are only given percent composition...you can only solve for the empirical formula
How many zeroes are in Avogadro's number?
What is...
22!
6 0 2 000,000,000,000,000,000,000
This refers to the actual chemical formula for a compound
what is...
the molecular formula.
If a 13 gram sample contains magnesium and oxygen decomposes, 5 grams of oxygen is obtained. What is the percent composition of the compound?
What is...
38.5% Oxygen; 61.5% Magnesium
***fine the mass of all the elements, then find the percents (percent/whole)
Convert 3.05 x 1025 atoms of Carbon to grams of Carbon.
What is...
608.5 grams
***if "moles" is not listed in the problem, it is most likely a 2-step conversion problem
A sample has a total mass of 3.585 grams and contains 1.388 grams of C, 0.345 grams of H, and 1.850 grams of O. What is its empirical formula?
What is...
CH3O
***we know that we must have percent composition to calculate empirical formula...so we must find percent composition first
How do you balance the following equation?
C3H8 + O2 ----------> CO2 + H2O
What is...
2 C3H8 + 10 O2 ----------> 6 CO2 + 8 H2O
(Don't worry...no balancing on the test!!)
This refers to the lowest whole-number ratio of the atoms or moles of the element.
what is...
the empirical formula
Calculate the mass of Carbon and Hydrogen in 82.0 grams of propane (C3H8).
(Hint: First find percent composition of propane)
What is... 67 grams of Carbon and 15 grams of Hydrogen.
***When a problem asks for mass of elements and all that is given is the mass of a sample of the compound, first find percent composition of the elements, then multiply percent composition by the grams of sample (82.0).
Convert 3 L of H2 gas to grams of H2 gas.
What is...
0.27 grams of H2 gas
***Remember...if there "moles" is not in the problem, it is a 2-step conversion problem.
The percent composition of methyl butanoate is 58.8% Carbon, 9.9% Hydrogen, and 31.3% Oxygen. The molecular mass of the compound is 306 g/mole. What is the molecular formula of the compound?
What is...
C15H30O6
***To calculate the molecular formula, you need the empirical formula and the molar mass. So we need to first find the empirical formula here. We always calculate the empirical using percent composition.