Potassium nitrate decomposes on heating, producing potassium oxide and gaseous nitrogen and oxygen:
4KNO3(s)--> 2K2O(s) + 2N2(g) + 5O2(g)
To produce 56.6 kg of oxygen, how many (a) moles of KNO3 must be heated? (b) Grams of KNO3 must must heated?
Here is a worked example of a stoichiometry problem such as this one.
http://www.jiskha.com/science/chemistry/stoichiometry.html
To determine the number of moles of KNO3 that must be heated to produce 56.6 kg of oxygen, we can use the stoichiometry of the reaction.
(a) Moles of KNO3:
From the balanced equation, we can see that 5 moles of O2 is produced for every 4 moles of KNO3.
Therefore, the molar ratio of O2 to KNO3 is 5:4.
To find the number of moles of KNO3, we can set up a proportion using this molar ratio:
(5 moles O2 / 4 moles KNO3) = (56.6 kg O2 / x moles KNO3)
Cross-multiplying and solving for x, we get:
x = (4 moles KNO3 / 5 moles O2) * (56.6 kg O2)
x ≈ 45.28 kg KNO3
Therefore, approximately 45.28 kg of KNO3 must be heated to produce 56.6 kg of O2.
(b) Grams of KNO3:
To convert the mass of KNO3 from kilograms to grams, we can use the conversion factor:
1 kg = 1000 grams
Therefore, the grams of KNO3 is:
45.28 kg * 1000 g/kg
= 45,280 grams
Therefore, approximately 45,280 grams of KNO3 must be heated.
To determine the number of moles and grams of KNO3 that must be heated to produce 56.6 kg of oxygen, we can use the balanced chemical equation provided.
(a) Moles of KNO3:
From the balanced equation, we can see that the molar ratio between KNO3 and O2 is 4:5. This means that for every 4 moles of KNO3, we will produce 5 moles of O2.
So, we can set up a proportion to find the number of moles of KNO3:
4 mol KNO3 / 5 mol O2 = x mol KNO3 / 56.6 kg O2
To solve for x, we need to convert 56.6 kg of O2 to moles. The molar mass of O2 is 32 g/mol (2*16). Therefore, the number of moles of O2 can be found as follows:
56.6 kg O2 * (1000 g/1 kg) * (1 mol/32 g) = 1768.75 mol O2
Now, we can solve for x:
4/5 = x/1768.75
x = (4/5) * 1768.75
x ≈ 1415 mol KNO3
Therefore, to produce 56.6 kg of oxygen, approximately 1415 moles of KNO3 must be heated.
(b) Grams of KNO3:
To find the grams of KNO3, we can use the molar mass of KNO3, which is 101.10 g/mol (39 + 14 + (3*16)).
Grams of KNO3 = moles of KNO3 * molar mass of KNO3.
Grams of KNO3 = 1415 mol KNO3 * 101.10 g/mol
Grams of KNO3 ≈ 142,981.50 g
Therefore, approximately 142,981.50 grams of KNO3 must be heated to produce 56.6 kg of oxygen.