OCR Gateway GCSE Chemistry PAGs: Separating Techniques, Distillation, Production of Salts and Rate of Reaction

How do you carry out evaporation?

Place the solution in an evaporating basin and gently heat with a Bunsen burner.

How do you separate an insoluble solid from a liquid?

Filtration: Place filter paper into a funnel, place the funnel in a beaker, and pour the solution into the funnel. Solid remains in the filter paper.

How do you separate a soluble solid from a solution?

Evaporation: Warm the solution in an evaporating basin using a Bunsen burner. Liquid evaporates, leaving the solid in the basin.

How could you separate a soluble solid from a solution, if the solid decomposes when heated?

Crystallisation: Pour the solution into an evaporating dish and heat gently. When crystals start to form, remove from heat and let cool. Filter the crystals and dry them.

How would you separate coloured soluble substances?

Chromatography: Place a spot of the sample on a pencil line 2cm from the bottom of chromatography paper and place it in a beaker of solvent (solvent level must be below pencil line).

What are the 2 phases in chromatography?

Mobile phase - solvent that carries substances; Stationary phase - paper or thin layer of an inert substance on a glass plate.

What affects how long molecules spend in each phase in paper chromatography?

Solubility in mobile phase and attraction to stationary phase.

Why should the line be drawn onto chromatography paper in pencil?

Pencil doesn't travel up the paper, whereas pen ink would.

Why are ink spots placed above the level of solvent in the beaker?

To prevent the ink from dissolving in the solvent rather than moving up the chromatography paper.

Why should chromatography paper be removed from the solvent before the solvent front reaches the top?

To allow the distance moved by the solvent to be measured for calculating the Rf value.

How do you calculate the Rf value?

Rf = Distance travelled by substance / Distance travelled by solvent; Rf is between 0 and 1.

What affects the Rf value?

The solvent and the stationary phase; changing these will change the Rf value.

What is the purpose of simple distillation and fractional distillation?

Simple distillation separates one liquid from a solution; fractional distillation separates several different liquids.

Describe how to carry out simple distillation.

Heat a solution in a round-bottomed flask using a Bunsen burner. The solvent evaporates, cools in the condenser, and the pure liquid is collected in a beaker.

How do you set up a condenser for simple distillation?

The condenser should be horizontal with water in at the bottom and out at the top.

Describe how to carry out fractional distillation.

Heat the mixture. Vapors rise up a column and condense when the temperature is below their boiling point. Liquids flow out.

How do you carry out evaporation?

Place solution in an evaporating basin and gently heat with a Bunsen burner.

How do you separate an insoluble solid from a liquid?

Filtration: Place filter paper into a funnel, pour the solution into the funnel, and the solid remains in the filter paper.

How do you separate a soluble solid from a solution?

Evaporation: Warm the solution in an evaporating basin with a Bunsen burner; the liquid evaporates, leaving the solid.

How could you separate a soluble solid from a solution if the solid decomposes when heated?

Crystallisation: Pour the solution into an evaporating dish, heat gently until crystals form, then filter and dry the crystals.

How would you separate coloured soluble substances?

Chromatography: Place a spot of the sample on a pencil line on chromatography paper and place it in a beaker of solvent.

What are the 2 phases in chromatography?

Mobile phase - solvent carrying substances; Stationary phase - paper or inert substance on a glass plate.

What affects how long molecules spend in each phase in paper chromatography?

Solubility in the mobile phase and attraction to the stationary phase.

Why should the line be drawn onto chromatography paper in pencil?

Pencil doesn't travel up the paper, unlike pen ink.

Why are ink spots placed above the level of solvent in the beaker?

To prevent the ink from dissolving in the solvent instead of moving up the chromatography paper.

Why should chromatography paper be removed from the solvent before the solvent front reaches the top?

To measure the distance moved by the solvent for calculating the Rf value.

How do you calculate the Rf value?

Rf = Distance travelled by substance / Distance travelled by solvent, with Rf between 0 and 1.

What affects the Rf value?

The solvent and the stationary phase; changing these will change the Rf value.

What is the purpose of simple distillation and fractional distillation?

Simple - to separate one liquid from a solution; Fractional - to separate several different liquids.

Describe how to carry out simple distillation.

Heat a solution in a round bottomed flask with a Bunsen burner; the solvent evaporates, cools in the condenser, and the pure liquid is collected.

How do you set up a condenser for simple distillation?

The condenser should be horizontal with water entering at the bottom and exiting at the top.

Describe how to carry out fractional distillation.

Heat the mixture; vapors rise up a column and condense when the temperature is below their boiling point, with liquids flowing out.

List precautions to take when using a Bunsen burner.

Don't leave unattended, turn off gas or leave on orange safety flame when not in use, tie back long hair, and work in a clear space.

How do you carry out evaporation?

Place solution in an evaporating basin and gently heat with a Bunsen burner.

How do you separate an insoluble solid from a liquid?

Filtration: Place filter paper into a funnel, pour the solution into the funnel, and the solid remains on the filter paper.

How do you separate a soluble solid from a solution?

Evaporation: Warm the solution in an evaporating basin until the liquid evaporates, leaving the solid behind.

How could you separate a soluble solid from a solution, if the solid decomposes when heated?

Crystallisation: Pour the solution into an evaporating dish, heat gently, remove from heat when crystals form, filter the crystals, and leave to dry.

How would you separate coloured soluble substances?

Chromatography: Place a spot of the sample on a pencil line on chromatography paper and place it in a beaker of solvent.

What are the 2 phases in chromatography?

Mobile phase: solvent carrying substances; Stationary phase: paper or thin layer of inert substance.

What affects how long molecules spend in each phase in paper chromatography?

Solubility in the mobile phase and attraction to the stationary phase.

Why should the line be drawn onto chromatography paper in pencil?

Pencil doesn't travel up the paper, whereas pen ink would.

Why are ink spots placed above the level of solvent in the beaker?

To prevent the ink from dissolving in the solvent instead of moving up the chromatography paper.

Why should chromatography paper be removed from the solvent before the solvent front reaches the top?

To measure the distance moved by the solvent for calculating the Rf value.

How do you calculate the Rf value?

Rf = Distance travelled by substance / Distance travelled by solvent (Rf is between 0 and 1).

What affects the Rf value?

The solvent and the stationary phase; changing these will change the Rf value.

What is the purpose of simple distillation?

To separate one liquid from a solution.

What is the purpose of fractional distillation?

To separate several different liquids.

Describe how to carry out simple distillation.

Heat a solution in a round-bottomed flask, the solvent evaporates, cools in the condenser, and the pure liquid is collected.

How do you set up a condenser for simple distillation?

The condenser should be horizontal with water in at the bottom and out at the top.

Describe how to carry out fractional distillation.

Heat the mixture, vapors rise up a column, condense below their boiling point, and liquids flow out.

What apparatus are used to record mass, time, and temperature?

Mass: balance; Time: stopwatch; Temperature: thermometer.

Give 2 ways of measuring a volume of liquid.

Pipette or measuring cylinder.

Give 1 way of measuring a volume of gas.

Gas syringe or upside-down measuring cylinder.

How can pH be measured?

Use a pH probe or universal indicator compared to a colour chart.

List safety precautions when purifying a salt.

Don't leave the Bunsen burner flame unattended, keep flammable chemicals away from the flame, and wear safety goggles and gloves.

What are the 2 processes needed to obtain a pure dry sample of salt?

Filtration and evaporation or crystallisation.

List precautions to take when using a Bunsen burner.

Don't leave unattended, turn off gas or leave on orange safety flame, tie back long hair, and keep flammable chemicals away from the flame.

What apparatus is used to record mass?

Balance

What apparatus is used to record time?

Stopwatch

What apparatus is used to record temperature?

Thermometer

What are two ways to measure the volume of a liquid?

Pipette or measuring cylinder

What is one way to measure the volume of a gas?

Gas syringe or upside-down measuring cylinder

Why must the bung be immediately attached to the reaction vessel when measuring gas volume?

To ensure minimal gas escapes

What two values are needed to calculate the change in temperature?

Initial temperature and final temperature

How can the rate of a reaction be measured?

By measuring change in mass, measuring the volume of gas produced, or observing colour change/precipitate formed.

When can the change in mass be used to measure the rate of a reaction?

When a gas is produced, as mass will decrease due to gas escaping.

How can the rate of reaction be measured if a precipitate is produced?

By placing a piece of paper with a black cross below the reaction vessel and observing how long it takes for the cross to disappear.

Why is the precipitate method not a reliable way to measure rate?

It is subjective; people might disagree on when the mark disappears or the solution changes colour.

How can you measure the rate of reaction if the coloured reactants form a colourless solution?

By timing how long it takes for the reactants to turn colourless.

How do you know that a reaction is complete?

When the mass of the reaction mixture, volume of gas, or colour remains the same.

What is the equation for the reaction between sulfuric acid and magnesium carbonate?

MgCO3 + H2SO4 → MgSO4 + CO2 + H2O

List four ways in which the rate of a reaction can be increased.

Increase surface area of reactants, use a catalyst, increase temperature, increase pressure/concentration.

What is a catalyst?

A substance which increases the rate of a reaction without being used up.

How does temperature affect the rate of a reaction?

Increasing temperature increases the rate because particles have more kinetic energy and move faster, leading to more frequent and successful collisions.

How does concentration of reactants affect the rate of a reaction?

Increasing concentration increases the rate because there are more particles in the same volume, leading to more frequent collisions.

How does using a catalyst affect the rate of a reaction?

Using a catalyst increases the rate by lowering the activation energy, allowing more collisions to exceed the activation energy.

How do you calculate the rate of reaction?

Rate of Reaction = Amount of product formed or reactant used ÷ Time.

How could you investigate how HCl concentration affects the rate of reaction with magnesium?

By measuring the volume of gas produced in a gas syringe every 10 seconds after adding magnesium to HCl and comparing rates for different concentrations.

How can you measure the rate of reaction when there is a change in mass?

By using a mass balance to measure initial mass and taking measurements at regular intervals as the reactants react.

How can you measure the rate of reaction when a gas is given off?

By attaching a gas syringe to a conical flask immediately after adding reactants and taking regular measurements of the gas volume.