Stoichiometry-I have the basic strategy, but am still stuck on how to do them.example...propane burns in oxygen according to the following reaction
C3H8 + O2 produces CO2 + H20
a. How many moles of CO2 are formed when 2.8 g of propane reacts?
b. If 0.45 g of oxygen is used in the burning of propane, how many moles of each CO2 and H2O are produced?
Here are the steps (at the last of the post)
Stoichiometry-I have the basic strategy, but am still stuck on how to do them.example...propane burns in oxygen according to the following reaction
C3H8 + O2 produces CO2 + H20
a. How many moles of CO2 are formed when 2.8 g of propane reacts?
b. If 0.45 g of oxygen is used in the burning of propane, how many moles of each CO2 and H2O are produced?
Step 1. Write and balance the equation.
C3H8 + 5O2 ==> 3CO2 + 4H2O
Step 2. Convert 2.8 g propane to moles. moles = g/molar mass.
2.8/44 = 0.636 moles propane
Step 3. Using the coefficients in the balanced equation, convert moles of what you have (in this case propane) to moles of what you want (in this case CO2).
moles CO2 = mols propane x (3 moles CO2/1 mol C3H8) = 0.636 x (3/1) = 0.19 moles CO2.[Note how the unit you don't want cancels and leaves the unit you want to convert to).
Step 4. Most problems ask for grams of the product (this one--part a-- just asked for moles) but if you want grams, then grams CO2 = moles x molar mass = 0.19 x 44 = 8.4 grams. You need to go through this because I estimated the molar masses and rounded here and there. At the end you need to round the answer to 2 significant figures (in line with the two s.f. in 2.8 g propane).
Part b is done the same way but that question asks for grams so you will need to use the fourth step. This procedure also will do limiting reagent problems if you throw in an extra step or two as sub parts of steps 2 and 3.
To solve stoichiometry problems like these, you need to follow a few steps. Let's go through the process step by step to solve both parts (a) and (b) of the question.
Step 1: Write down the balanced equation for the reaction. The given balanced equation is:
C3H8 + O2 → CO2 + H2O
Step 2: Identify the information given in the problem and convert it to moles if necessary. In part (a), you are given the mass of propane (C3H8), and in part (b), you are given the mass of oxygen (O2). You'll need to convert these masses to moles.
To convert the mass of a substance to moles, you use the molar mass. The molar mass of an element or compound is the mass of one mole of that substance. You can find the molar mass by looking up the atomic masses of the elements from the periodic table.
The molar mass of propane (C3H8) is calculated by adding up the atomic masses of carbon (C) and hydrogen (H), each multiplied by their respective subscripts:
Molar mass of C3H8 = (3 * atomic mass of C) + (8 * atomic mass of H)
Similarly, the molar mass of oxygen (O2) is calculated as:
Molar mass of O2 = (2 * atomic mass of O)
Step 3: Use stoichiometry ratios to calculate the desired quantity. In each case, you need to find the number of moles of CO2 (part (a)) or both CO2 and H2O (part (b)) produced.
(a) How many moles of CO2 are formed when 2.8 g of propane reacts?
To solve part (a):
1. Convert the given mass of propane to moles using its molar mass.
2. Use the stoichiometry ratio from the balanced equation to find the moles of CO2 produced.
Step 4: Calculate the moles of the desired substance using the stoichiometry ratio. In this case, the ratio of moles of propane (C3H8) to moles of CO2 is 1:1, based on the balanced equation.
(a) Solution:
1. Calculate the molar mass of propane (C3H8) using the periodic table.
2. Convert the given mass of propane (2.8 g) to moles:
Moles of C3H8 = Given mass / Molar mass
3. Use the stoichiometry ratio of 1:1 to find the moles of CO2 produced:
Moles of CO2 = Moles of C3H8
(b) If 0.45 g of oxygen is used in the burning of propane, how many moles of each CO2 and H2O are produced?
To solve part (b):
1. Convert the given mass of oxygen (O2) to moles using its molar mass.
2. Use the stoichiometry ratio from the balanced equation to find the moles of CO2 and H2O produced.
Step 4: Calculate the moles of desired substances using the stoichiometry ratio. In this case, the ratio of moles of oxygen (O2) to moles of CO2 is 1:1, and the ratio of moles of oxygen (O2) to moles of H2O is 1:4, based on the balanced equation.
(b) Solution:
1. Calculate the molar mass of oxygen (O2) using the periodic table.
2. Convert the given mass of oxygen (0.45 g) to moles:
Moles of O2 = Given mass / Molar mass
3. Use the stoichiometry ratios to find the moles of CO2 and H2O produced:
Moles of CO2 = Moles of O2
Moles of H2O = Moles of O2 * 4 (since the ratio is 1:4)
Following these steps should help you calculate the number of moles of CO2 and H2O produced in the given reactions.