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Example Questions
Example Question #11 : Concentration And Units
A chemist wants to turn a 50.0mL solution of into a solution. How much water should she add?
To solve this problem, we may use the following equation relating the molarity and volume of two solutions:
Recall:
Plug in known values and solve.
However, this is not the final answer. The whole volume of the second, 0.4M solution is 85mL. Thus the chemist needs to add 25mL of water to the original solution to obtain the desired concentration.
Example Question #386 : Ap Chemistry
In order to dilute a 1mL solution that is 0.01M so that the solution is diluted to , how many milliliters does this solution need to be diluted to?
Use the dilution formula:
Rearranging this equation gives:
Plugging in the values gives:
Example Question #383 : Ap Chemistry
What concentration would you have prepared if you diluted 30mL of a 0.350M salt solution to 50mL?
Use the dilution formula:
Rearranging this equation gives:
Plugging in the values gives:
Therefore, after diluting the solution to 50mL, the solution concentration would be lowered from 0.35M to 0.21M.
Example Question #32 : Solutions
How many moles are in a 0.010L solution with a concentration that is ?
By using the concentration as a conversion factor, the number of moles can calculated by multiplying the concentration by the number of liters.
Therefore, there are in of a solution.
Example Question #31 : Solutions
In order to prepare a needed solution for an experiment, 0.082 grams of was dissolved in water to give a 35mL solution. What is the molarity of this solution?
In order to calculate the concentration, we must use molarity formula:
We must use the molecular weight of sodium chloride to calculate the moles of solute:
Therefore, the concentration in molarity of this solution is 0.040M.
Example Question #34 : Solutions
How many moles are in 1000mL solution with a concentration that is ?
By simply using the concentration as a conversion factor, the number of moles can be calculated by multiplying the concentration by the number of liters. Before calculating the number of moles, the number of milliliters must be converted to liters using the fact that .
Therefore, there are in of a solution.
Example Question #1 : Precipitates And Calculations
A chemist combines 300 mL of a 0.3 M solution with 200 mL of 0.4 M solution. How many grams of precipitate form?
No precipitate is formed
First, let us write out an ion exchance reaction for the reactants:
By solubility rules, is soluble in water and is not. Our new reaction is:
Now we will calculate the theoretical yield of each reactant.
Now we perform the same calculation beginning with :
The limiting reagent is and this reaction produces 18.7 g precipitate.
Example Question #2 : Precipitates And Calculations
A chemist boils off the water from 234 mL of a 0.4 M solution of KCl. What is the mass of the remaining solid?
None of the available answers
Example Question #2 : Precipitates And Calculations
A chemist boils off 344 mL of a 0.35 M solution of sodium hydroxide. How much solid remains?
No solid will remain as it will boil off with the water
None of the available answers
First, you must recognize that the chemical formula for sodium hydroxide is . The mass of the boiled solution is
Example Question #31 : Solutions
What is the mass of the solid left over after boiling off 100mL of 0.4M NaCl solution?
None of the available answers
The remaining mass with be equal to the mass of the sodium chloride in the solution. Once the solvent (water) evaporates, the solute will remain.
Atomic mass of sodium is ~23. Atomic mass of chlorine is ~35.5. Molecular mass of NaCl is ~58.5.
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