Describe the test for chlorine gas. Give the positive result.
Use damp litmus paper; it bleaches white.
What is a formulation?
A mixture that has been designed as a useful product made from specific chemicals in measured quantities.
Describe the test for hydrogen gas. Give the positive result.
Use a lit splint; it burns rapidly with a pop sound.
State the equation used to calculate an Rf value.
Rf = Distance moved by substance ÷ Distance moved by solvent.
Describe how you can test to see if a substance is pure. Give the positive result.
Melt or boil it; a pure substance has a specific, fixed melting/boiling point.
Name two examples of formulations.
Paint, fertilizer, medicine, fuel, cleaning products, food, alloys.
How many spots will a pure substance produce on a chromatogram?
One.
Name one change that could be made in chromatography that will change an Rf value for the same substance.
Use a different solvent or different chromatography paper.
0.725 mol of reactant is used up in 20s. Calculate the rate of the reaction, including the unit.
0.725 ÷ 20 = 0.03625 mol/s
How can the rate of a reaction at a specific time be calculated from a graph?
Draw a tangent to the curve at that time, use the tangent to make a right-angled triangle, find the change in y and change in x, then calculate the gradient of the tangent.
Name a piece of equipment needed to measure a volume of gas.
Inverted measuring cylinder (in water) or gas syringe.
Define activation energy.
The minimum amount of energy needed for particles to react.
Explain how increasing concentration affects the rate of a reaction.
It increases the number of particles in the same volume, increases frequency of collisions, and increases the rate of reaction.
Explain the effect adding a catalyst has on the position of equilibrium.
No effect, as the rate of the forward and reverse reactions increase by the same amount.
What effect will decreasing the pressure have on a reversible reaction?
The position of equilibrium will shift to the side with the most gas molecules.
