Questions: Measurement and Matter
Adding or subtracting and multiplying or dividing measurements
Samanthe
A chemistry student must write down in her lab notebook the concentration of a solution of sodium thiosulfate. The concentration of a solution equals the mass of what's dissolved divided by the total volume of the solution.
Here's how the student prepared the solution:
- The label on the graduated cylinder says:
empty weight: 3.050 g
- She put some solid sodium thiosulfate into the graduated cylinder and weighed it. With the sodium thiosulfate added, the cylinder weighed 28.4 g.
- She added water to the graduated cylinder and dissolved the sodium thiosulfate completely. Then she read the total volume of the solution from the markings on the graduated cylinder. The total volume of the solution was 40.5 mL.
What concentration should the student write down in her lab notebook? Be sure your answer has the correct number of significant digits.
g · mL^-1
Transcript text: Measurement and Matter
Adding or subtracting and multiplying or dividing measurements
Samanthe
A chemistry student must write down in her lab notebook the concentration of a solution of sodium thiosulfate. The concentration of a solution equals the mass of what's dissolved divided by the total volume of the solution.
Here's how the student prepared the solution:
- The label on the graduated cylinder says:
empty weight: 3.050 g
- She put some solid sodium thiosulfate into the graduated cylinder and weighed it. With the sodium thiosulfate added, the cylinder weighed 28.4 g .
- She added water to the graduated cylinder and dissolved the sodium thiosulfate completely. Then she read the total volume of the solution from the markings on the graduated cylinder. The total volume of the solution was 40.5 mL .
What concentration should the student write down in her lab notebook? Be sure your answer has the correct number of significant digits.
$\square$ $\mathrm{g} \cdot \mathrm{mL}^{-1}$ $\square$ ■
Solution
Solution Steps
Step 1: Determine the Mass of Sodium Thiosulfate
First, we need to find the mass of the sodium thiosulfate by subtracting the empty weight of the graduated cylinder from the weight of the cylinder with the sodium thiosulfate.
The mass of sodium thiosulfate (25.35 g) has 4 significant digits, and the volume (40.5 mL) has 3 significant digits. The result should be reported with the least number of significant digits, which is 3.