CHEM 1001 Lab 2: Solutions and Dilutions

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Questions and Answers

What is the first step when preparing a solution in a beaker?

Add the solute to the volumetric flask.

Add approximately half of the required volume of solvent to the solute in the beaker. (correct)

Stir the solute with distilled water until mixed.

Rinse the beaker with distilled water.

What method is used to transfer the solution from the beaker to the volumetric flask?

Simplified transfer method with no rinsing.

QUANTITATIVE transfer method. (correct)

Direct transfer method.

An improper method that involves pouring directly.

How should the volumetric flask be mixed after adding the final solvent?

Stir with a glass rod until dissolved.

Mix by slow inversion. (correct)

Shake vigorously for 30 seconds.

Swirl the flask for 2 minutes.

What must be included when labeling a centrifuge tube?

Solute name, solvent, final concentration, date, and name. Signup and view all the answers

What is the appropriate disposal method for liquid waste in this lab?

Use the waste container in the fume hood. Signup and view all the answers

What is the difference between a solute and a solvent in a solution?

The solute is the substance dissolved in the solvent, which is present in greater quantity. Signup and view all the answers

What does a 1%(w/v) solution imply in practical terms?

1g of solute in 100mL of solvent. Signup and view all the answers

How is concentration mathematically defined for a solution?

C = m/V Signup and view all the answers

Which of the following balances provides the highest measurement accuracy?

Analytical Balance (±0.0005g) Signup and view all the answers

What is the acceptable range for reported values using a rough/top-loading balance?

±0.01g Signup and view all the answers

What is the concentration of Solution 1 in g/100mL?

0.1 g/100mL Signup and view all the answers

Which equipment is essential for measuring the solute accurately?

Analytical balances Signup and view all the answers

What volume of distilled water is required to prepare Solution 2 with a concentration of 0.1775 %(w/v)?

50 mL Signup and view all the answers

What is the first step in preparing the solutions?

Rinse glassware with distilled water Signup and view all the answers

Which solution contains the highest concentration by mass?

Solution 2 Signup and view all the answers

In the preparation of solutions, what does the term 'solute' refer to?

The substance being dissolved Signup and view all the answers

What is the purpose of rinsing the weigh boat with distilled water?

To ensure all dye is transferred to the beaker Signup and view all the answers

The concentration of Solution 3 can be described as which of the following?

0.0585 g/100mL Signup and view all the answers

What is the primary function of a balance in scientific measurements?

To measure the amount of matter an object contains Signup and view all the answers

How does the weight of an object differ from its mass?

Mass remains the same regardless of location, while weight can change based on gravity. Signup and view all the answers

Which type of balance has the highest sensitivity?

Analytical balance Signup and view all the answers

What distinguishes a rough/top-loading balance from an analytical balance?

Top-loading balances have lower sensitivity compared to analytical balances. Signup and view all the answers

Why should scientific balances be treated with care?

They are sensitive equipment that can be easily damaged. Signup and view all the answers

In which context is the concept of mass particularly important?

When determining the amount of matter in space Signup and view all the answers

What characteristics are unique to mechanical balances?

They consist of moving parts like fulcrums and springs. Signup and view all the answers

Which statement about mass and weight is correct?

Mass does not change regardless of location, while weight depends on gravity. Signup and view all the answers

Study Notes

Measuring Mass

Distinction between scales (measurements based on a calibrated range) and balances (instruments for measuring mass).
Mass refers to the amount of matter in an object, whereas weight measures the gravitational force on that object.
Mass remains constant regardless of location, while weight varies with gravitational influence (e.g., rhinoceros on Earth vs. Moon).
Balances are classified into mechanical (useful parts) and electronic (minimal moving parts).
Further classification of balances into rough/top-loading (sensitivity ±0.01g) and analytical (sensitivity ±0.0001g).
Lab involves measuring mass using various balances; instructor demonstrates proper handling.

Preparing Solutions

Solution is a homogeneous mixture of solute (lesser amount) and solvent (greater amount) with uniform properties.
Concentration expressed by the formula C = m/V (mass of solute per volume of solvent).
% (w/v) concentration notation represents grams of solute per 100 mL of solvent.
Example: 1% (w/v) solution = 1g solute in 100mL solvent.

Solutions to Prepare

Solution 1: 0.10% (w/v), 100 mL, equivalent to 0.10 g/100 mL.
Solution 2: 0.1775% (w/v), 50 mL, equivalent to 0.1775 g/100 mL.
Solution 3: 0.0585% (w/v), 250 mL, equivalent to 0.0585 g/100 mL.

Preparation Procedure

Calculations for solute amounts performed by the instructor before class begins.
Rinse all glassware with distilled water to avoid contamination.
Measure out the solute on an analytical balance using a weigh boat, then transfer to a beaker.
Add approximately half the required solvent, stir until completely dissolved.
Transfer contents to a volumetric flask using the quantitative transfer technique, ensuring no residue is left.
Fill the volumetric flask to the etched line with solvent and mix by gentle inversion.
Label a 50 mL centrifuge tube with solute type, solvent, concentration, date, and name before transferring solution.
Repeat the procedure for each solution required for future labs.

Waste Disposal

Dispose of liquid waste in the designated container within the fume hood.
Dispose of weigh boats in the large biohazard container.

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Description

This quiz focuses on the essential concepts of measuring mass, specifically distinguishing between scales and balances in a chemistry lab setting. Understand the fundamental terms that are crucial for conducting experiments with solutions and dilutions. Test your knowledge and prepare for practical applications in lab work.