18 Questions
What is the percentage atom economy in forming ethene by the given reaction?
28.3%
Calculate the molar mass of hydrogen chloride (HCl).
36.5 g/mol
In a chemical reaction, 5.8g of water (H2O) is produced. If the molar mass of water is 18 g/mol, how many moles of water were produced?
0.322 moles
A solution of ZnSO4 has a concentration of 0.045963 mol/L. What volume of the solution contains 2 moles of ZnSO4?
43.7 L
Calculate the percentage yield if the expected yield is 10g and the actual yield obtained is 7g.
70%
In a titration, if it took 25mL of a 0.1 M NaOH solution to neutralize 30mL of an unknown HCl solution, what is the concentration of the HCl solution?
0.0833 M
What is the molar ratio between NaOH and HCl in the given reaction?
1:1
In the reaction, if 0.045 moles of NaOH were used, what would be the volume of HCl needed to neutralize it?
50 cm³
What is the theoretical yield of NaCl if 2.0 g of NaOH and excess HCl are used in the reaction?
3.0 g
If the percentage yield for a reaction is 85%, what would be the actual yield if the theoretical yield is 6.5 g?
7.5 g
Given that the molar mass of O₂ is 32 g/mol, how many moles of O₂ are produced from 4.0 g of KClO₃?
0.125 moles
If a reaction has a theoretical yield of 18 g and an actual yield of 15 g, what is the percentage yield?
80%
What is the rearranged equation for percentage yield?
Actual yield = (% yield / 100) x theoretical yield
What is the first step in calculating the percentage yield of a reaction?
Work out the number of moles of the reactant
In the given reaction, how many grams of magnesium oxide should theoretically be produced?
3.83 g
What does atom economy reflect in a chemical reaction?
Efficiency of a reaction producing desired products
How can you calculate the mass of a product in a chemical reaction?
Moles x Molar mass
What step is essential in determining the percentage yield using the rearranged equation?
Substitute values into the rearranged equation
Study Notes
Calculating Percentage Yield
- Rearrange the percentage yield equation to: Actual yield = (% yield / 100) x theoretical yield
- Use this rearranged equation to calculate the actual yield
Worked Exam Style Question
- Given the equation: 2Mg + O2 → 2MgO
- Calculate the percentage yield of the reaction, given that burning 2.32 g of magnesium produced 2.39 g of magnesium oxide
- Steps:
- Work out the number of moles of magnesium
- Calculate the theoretical yield of magnesium oxide
- Calculate the percentage yield
Atom Economy
- Atom economy reflects the efficiency of a reaction producing the desired product
- Calculate atom economy using the equation: Desired product / (Desired product + By-product) x 100
- Example 1: Calculate the atom economy for the reaction producing Mg(OH)2
- Desired product = Mg(OH)2, Mr = 58
- By-product = NaCl, Mr = 58.5
- Atom economy = 58 / 116.5 = 49.8%
Worked Exam Style Questions
- Calculate the atom economy for the reaction forming ethene: C12H26 → C10H22 + C2H4
- Steps:
- Work out the molecular mass of ethene
- Work out the molecular mass of decane
- Calculate the atom economy
- Steps:
Example Questions
- Calculate the atom economy for the reaction producing hydrogen chloride
- Steps:
- Work out the molecular mass of hydrogen chloride
- Use the atom economy equation to calculate the atom economy
- Steps:
This quiz covers the calculation of percentage yield in a chemical reaction scenario. It involves rearranging the percentage yield equation and substituting values to find the actual yield. The specific question provided involves calculating the percentage yield of a reaction between magnesium and oxygen.
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