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Student Page 3.7.4 Chemistry Mixture Problems Using Quantity Rate Value Tables
A4US

Quantity Rate Value Tables are helpful in setting up equations to solve mixture problems in chemistry and other fields. As you solve these problems, notice that a Rate is needed in all three rows. Add Quantities and Values to obtain equations to solve these problems.

1.

How much 10% sulfuric acid (\(H_2SO_4\)) must be mixed with how much 30% sulfuric acid to make 200 milliliters of 15% sulfuric acid?

(a)

Fill in the first two rows of Table 3.7.4.1 using information from the problem.

Table 3.7.4.1. QRV Table For Acids
  Quantity Rate Value
Weak Acid      
Strong Acid      
Total      
(b)

Define your variables. Be specific about what each one means.

(c)

Determine equations arising from the table.

(d)

Solve the system of equations. Show your work. Show that your solution works.

(e)

Interpret your solution based on the problem with two different strengths of acid solution.

2.

Solve these two problems similarly to problem 1. Draw your own table for each problem.

(a)

You need 20 liters of 20% acid solution. You have jugs of 10% solution and 25% solution. How many liters of each should you combine to get the needed solution?

(b)

A medical technician has 20% alcohol solution and 70% alcohol solution. She needs 20 liters of a 40% alcohol solution. What amount of each type of solution should she combine?

3.

For each problem, add Quantities to get an expression. Add Values to get another expression. Use the rate for the Total row to find a relationship between the expressions.

(a)

A chemist has 6 liters of a 25% alcohol solution. How much alcohol must he add so that the resulting solution contains 50% alcohol?

Table 3.7.4.2. QRV Table For Alcohol
  Quantity Rate Value
Weak Acid      
Strong Acid      
Total      
(b)

How many liters of a 14 percent alcohol solution must be mixed with 20 liters of a 50 percent alcohol solution to get a 20 percent alcohol solution? (Draw your own table.)

4.

Sterling Silver is 92.5% pure silver. How many grams of pure silver and sterling silver must be mixed to obtain 100g of a 94% Silver alloy?

Table 3.7.4.3. QRV Table For Silver
  Quantity Rate Value
Sterling Silver      
Pure Silver      
Total