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Name:………………………………
Grade: ……………10…………..
Subject: Chemistry
Date ………………………
Chapter 11 :Stoichiometric
Section 2 : Stoichiometric calculations
Stoichiometric mole-to-mole conversion
Reaction between potassium and water 2K(s) + 2 H 2 O(l) → 2KOH(aq) + H 2 (g)
From the balanced equation, you know that two moles of potassium yield one mole of hydrogen.
Q1 : how much hydrogen is produced if only 0.0400 mol of potassium is used?
Because the given substance is in moles and the unknown substance to be determined is also in moles, this problem involves a mole-to-mole conversion.
To solve the problem, you need to know how the unknown moles of hydrogen are related to the known moles of potassium. Mole ratios are used as conversion factors to convert the known number of moles of one substance to the unknown number of moles of another substance in the same reaction.
Several mole ratios can be written from the equation, but the correct one is
So,
Known Unknown K= 0.0400 mole H2 = ? moles
Answer the following:
- For the following equation
C 3 H 8 (g) + O 2 (g) → C O 2 (g) + H 2 O(g)
How many moles of C O 2 are produced when 10.0 mol of C 3 H 8 are burned in excess oxygen in a gas grill?
The answer
1- Balance the equations 2- Follow the way shown above
So C 3 H 8 (g) + 5 O 2 (g) → 3C O 2 (g) + 4 H 2 O(g)
Known Unknown C 3 H 8 = 10.0 moles C O 2 = ? moles
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Stoichiometric mole-to-mass conversionNow, suppose you know the number of moles of a reactant or product in a reaction and you want to calculate the mass of another product or reactant. This is an example of a mole-to-mass conversion.
Example:Determine the mass of sodium chloride (NaCl), commonly called table salt, produced when 1.25 mol of chlorine gas ( Cl 2 ) reacts with sodium
The answer : 1- Write the balanced chemical equation
2Na(s) + C l 2 (g) → 2NaCl(s)2-
Known Unknown1.25 mol Cl2 ? grams of NaCl
3- Find the moles of NaCl by using mole ratio
4- Convert moles of NaCl to grams by multiplying by the molar mass
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