C6 Flashcards
What must chemists and engineers do before using chemicals and making new products?
Assess the rules.
What does chemical synthesis mean?
using simple substances to make new, useful chemical compounds.
The chemical industry uses chemical synthesis to..
make chemicals for food additives, fertilizers, dyes paints, pigments and medicines.
What does indicators do?
turn different colors into acids and alkali’s.
What color is litmus paper in acids and in alkali?
Red in acids
Blue in alkalis.
What color is universal indicator in acids and in alkali?
Orange or red in acids
Green or blue in alkalis
Pure acid compounds can be…
solids liquids or gases.
What do pure acid compounds dissolve in water to form?
dilute acids that can be tested using indicators.
What are 3 common alkali’s?
Sodium Hydroxide, potassium hydroxide and calcium hydroxide.
The pH scale is a measure of how….
strong an acid or alkali is.
How can pH be measured?
universal indicator or a pH meter.
Calcium + Hydrochloric acid——–>
Calcium chloride + Hydrogen
Magnesium Oxide + Sulfuric acid —–>
Magnesium sulfate + water + CO2
Salts are…
Ionic compounds.
What is neutralization?
When an acid reacts with an alkali, becoming neutral.
What is a titration used to measure?
to measure the volume of acid and alkali that react together.
What role does the indicator play in neutralization?
Used to tell when neutralisation happens by changing colour at the end point of titration
When an acid reacts with an alkali, what is made?
a salt and water.
What do all acids contain when they are dissolved in water?
Hydrogen ions (H+)
What is the pH of an acid related to?
the concentration of H+ ions in the acid solution.
What do all alkalis contain when they are dissolved in water?
Hydroxide Ions (OH-).
What is the general ionic equation for all neutralisation reactions?
H+(aq) + OH-(aq) —–>H20(I)
The positive ion from the alkali and negative ion from the acid make the…
salt.
Difference between exothermic and endothermic reactions?
Exothermic- give out heat energy. The temperature of the surroundings rises.
Endothermic- takes in heat energy. The temperature of the surroundings falls.
What is a ‘pure’ substance?
A substance with nothing else mixed with it.
In industry, pure substances need to be separated from…
impurities.
What is an ‘impurity’?
A left over reactant or other products.
What is filtration used for?
To separate a solid from a liquid or from a solution.
What is crystilisation used for?
to purify impure solid crystals.
What are the steps of crystallization?
- Dissolving
- Filtering
- Evaporating
- Filtering
- Drying
What is percentage yield?
Worked out from actual yield and the theoretical yield?
What is actual yield?
The mass product measured at the end of the experiment.
What is the theoretical yield?
the predicted yield. It is calculated from the amount of reactants used and the equation for the reaction.
What is the formula for percentage yield?
Percentage yield = actual yield/theoretical yield x 100%.
What is the rate of reaction?
The amount of product produced or the amount of reactant used up in a certain time. This is usually measured as the amount per second.
In industry, chemical engineers aim to produce the most amount in a…
minimal time.
How do chemical engineers aim to produce the most amount in a minimal time?
By changing conditions to make reactions faster and to make the process as economical as possible.
If the reaction makes a gas, the rate can be followed by:
- measuring the volume of gas made at set times, e.g. every 30 seconds.
- measuring the decrease in mass of the flask as the gas leaves the reaction.
What is a colorimeter used for?
To follow the rate of a colour change.
What does a rate of reaction graph show?
The change in the amount of reactant or product against the time.
The gradient of the curve at any point gives..
the rate of reaction.
The more collisions in a reaction, the…
faster the reaction.
A catalyst is a substance that…
speeds up a chemical reaction but is not used up.
Reactions are faster when:
- the temperature of the reactant increases.
- the size of solid particles are smaller, increasing the surface area).
- the concentration of reactants of changing in solution increases.
Acid + Metal —->
Salt + Hydrogen
Acid + Metal Oxide —->
Salt + Water
Acid + Metal Hydroxide —->
Salt + Water
Acid + Metal Carbonate —–>
Salt + Water + Carbon Dioxide
