Questions: Name: U6 WS 3 In the following situations, indicate whether or not the evidence suggests a chemical change. Include the evidence you used to make your decision. 1. The concentration of salt in human blood is about 9.0 g per liter. a. How many moles of sodium chloride (NaCl) are in 9.0 grams? b. If this mass were dissolved in 1.00 L of water, what would the molarity of the solution be? 2. A scientist has 1.00 L of a sodium chloride solution that is 0.50 M. What volume of this solution does she need to make 150 mL of a salt solution that has the same molarity of blood?

Name:
U6 WS 3
In the following situations, indicate whether or not the evidence suggests a chemical change. Include the evidence you used to make your decision.
1. The concentration of salt in human blood is about 9.0 g per liter.
a. How many moles of sodium chloride (NaCl) are in 9.0 grams?
b. If this mass were dissolved in 1.00 L of water, what would the molarity of the solution be?
2. A scientist has 1.00 L of a sodium chloride solution that is 0.50 M. What volume of this solution does she need to make 150 mL of a salt solution that has the same molarity of blood?

Transcript text: Name: U6 WS 3 In the following situations, indicate whether or not the evidence suggests a chemical change. Include the evidence you used to make your decision. 1. The concentration of salt in human blood is about 9.0 g per liter. a. How many moles of sodium chloride $(\mathrm{NaCl})$ are in 9.0 grams? b. If this mass were dissolved in 1.00 L of water, what would the molarity of the solution be? 2. A scientist has 1.00 L of a sodium chloride solution that is 0.50 M . What volume of this solution does she need to make 150 mL of a salt solution that has the same molarity of blood?

Solution

Solution Steps

Step 1: Calculate Moles of Sodium Chloride

Use the molar mass of sodium chloride $(\mathrm{NaCl})$, which is approximately 58.44 g/mol.
Calculate the number of moles in 9.0 grams using the formula: \[ \text{moles of NaCl} = \frac{\text{mass of NaCl}}{\text{molar mass of NaCl}} = \frac{9.0 \, \text{g}}{58.44 \, \text{g/mol}} \]

Step 2: Calculate Molarity of the Solution

Molarity is defined as moles of solute per liter of solution.
Use the moles calculated in Step 1 and the volume of the solution (1.00 L) to find the molarity: \[ \text{Molarity} = \frac{\text{moles of NaCl}}{1.00 \, \text{L}} \]

Step 3: Determine Volume Needed for Desired Molarity

Use the dilution formula $ C_1V_1 = C_2V_2 $, where:
- $ C_1 = 0.50 \, \text{M} $ (initial concentration)
- $ V_1 $ is the volume needed
- $ C_2 = 0.154 \, \text{M} $ (molarity of blood)
- $ V_2 = 150 \, \text{mL} = 0.150 \, \text{L} $
Solve for $ V_1 $: \[ V_1 = \frac{C_2 \times V_2}{C_1} = \frac{0.154 \, \text{M} \times 0.150 \, \text{L}}{0.50 \, \text{M}} \]