Core Practical: Investigating Rate of Reaction Flashcards

All 7 cards in this deck

In the marble chips and hydrochloric acid practical, what two pieces of apparatus are needed to collect and measure the gas?

A delivery tube with a bung in the flask, connected to a gas syringe (or leading into an upturned measuring cylinder of water in a trough).

Why does the mixture turn cloudy when sodium thiosulfate reacts with dilute hydrochloric acid?

A solid/precipitate of sulfur is formed.

In the 'disappearing cross' method (sodium thiosulfate + dilute hydrochloric acid), what is timed, and what does a shorter time show?

The time from mixing until the cross under the flask can no longer be seen (the sulfur precipitate hides it). A shorter time means a faster rate.

How can the conical flask and its contents be kept at a constant temperature such as 45°C during a rate investigation?

Stand the conical flask in a water bath.

In a rate investigation using calcium carbonate and hydrochloric acid at different temperatures, name three variables that must be controlled.

Particle size of the calcium carbonate, mass of calcium carbonate, and concentration (or volume) of acid.

Apart from collecting gas, state one other quantity that can be measured over time to follow the rate of a reaction that produces a gas.

The loss in mass of the reaction flask on a balance.

When following a rate by loss in mass, why is a loose plug of cotton wool put in the neck of the flask?

It lets the gas escape, so the mass falls, but stops liquid spraying out of the flask, which would also lose mass and give a false reading.