Two rates experiments

Describe the method to measure the rate of a reaction using the disappearing cross method.

Mix sodium thiosulfate and hydrochloric acid in a flask. Place it over a cross and time how long it takes for the cross to disappear due to the formation of sulfur.

What does the disappearing cross method measure?

The time taken for a precipitate to form, obscuring the cross.

Describe the method to measure the rate of a reaction using a gas syringe.

React a solid with a liquid (e.g., magnesium and acid) in a sealed flask, and collect the gas in a syringe to measure its volume over time.

What kind of data do you collect in the gas syringe method?

The volume of gas produced over time.

What is the role of concentration in the disappearing cross experiment?

To investigate how concentration affects the rate of reaction.

How do you ensure the experiment is fair in the disappearing cross method?

Keep the volume and temperature constant for all trials.

Why is it important to use the same concentration of reactants in a fair test?

To isolate the effect of one variable (e.g., temperature or surface area).

What safety precautions are necessary for the disappearing cross experiment?

Work in a well-ventilated area and wear goggles to protect against acid fumes.

Why is a conical flask used in both experiments?

It minimizes spillage and contains the reaction effectively.

What is the dependent variable in the gas syringe experiment?

The volume of gas collected.

What is the independent variable in the disappearing cross experiment?

The concentration of reactants or the temperature.

How does temperature affect the rate of reaction in the disappearing cross experiment?

Higher temperatures cause faster reactions, making the cross disappear sooner.

Why should the same person observe the cross disappearance?

To reduce subjective variation in when the cross is deemed "no longer visible."

What is the purpose of repeating both experiments?

To ensure reliability and average out anomalies.

How could the accuracy of the gas syringe experiment be improved?

Use a syringe with finer graduations for more precise measurements.