Quick Review Flashcards - Click to flip and test your knowledge!
Question
Which scientist synthesised water by igniting hydrogen and oxygen to prove it is a compound?
Answer
Henry Cavendish.
Question
In what ratio by volume are hydrogen and oxygen combined in a water molecule?
Answer
$2:1$.
Question
Why is water referred to as a 'universal solvent'?
Answer
It has the ability to dissolve a large number of substances, including solids, liquids, and gases.
Question
What is the characteristic particle size of a true solution?
Answer
Less than $1\text{ nm}$.
Question
Which type of mixture has a particle size ranging between $1\text{ nm}$ and $100\text{ nm}$?
Answer
Colloidal solution.
Question
In which type of mixture can particles be seen with the naked eye and settle down over time?
Answer
Suspension.
Question
A mixture where the constituents are uniformly mixed is described as _____.
Answer
Homogeneous.
Question
What term describes the substance that dissolves in a solvent to form a solution?
Answer
Solute.
Question
A solution in which the amount of solute is relatively large compared to the solvent is called a _____ solution.
Answer
Concentrated.
Question
What defines a saturated solution at a particular temperature?
Answer
A solution that cannot dissolve any more of the solute at that temperature.
Question
How can a saturated solution be converted into an unsaturated solution without adding more solvent?
Answer
By heating the solution slowly.
Question
What is a supersaturated solution?
Answer
A solution that contains more solute at a given temperature than what is present in a saturated solution.
Question
Which solvent is commonly used in laundries and dry cleaners to remove grease stains?
Answer
Petrol (or benzene/kerosene).
Question
Which solvent is used to prepare 'tincture of iodine'?
Answer
Alcohol.
Question
Term: Solubility
Answer
Definition: The maximum amount of solute in grams that will saturate $100\text{ g}$ of solvent at a specific temperature.
Question
State the mathematical formula used to calculate the solubility of a solute.
Answer
$\text{Solubility} = \frac{\text{Weight of solute [g]}}{\text{Weight of solvent [g]}} \times 100$.
Question
How does an increase in temperature typically affect the solubility of solids like $KNO_{3}$?
Answer
Solubility increases with the rise in temperature.
Question
Which salt shows a decrease in solubility as temperature increases above $70^{\circ}\text{C}$?
Answer
Calcium sulphate ($CaSO_{4}$).
Question
What is a solubility curve?
Answer
A graph showing the effect of temperature on the solubility of a specific substance.
Question
According to Henry's Law, how does pressure affect the solubility of a gas in a liquid?
Answer
The mass of gas dissolved is directly proportional to the pressure on the surface of the liquid.
Question
What effect does increasing temperature have on the solubility of gases in water?
Answer
It causes a decrease in the solubility of the gas.
Question
Why does boiled water often taste flat?
Answer
The dissolved gases (like air) that contribute to taste are expelled during boiling.
Question
Concept: Crystallisation
Answer
Definition: The process by which crystals are separated or deposited from a hot saturated solution of a substance upon cooling.
Question
What is a 'seed crystal'?
Answer
A well-formed crystal suspended in a cooled saturated solution to encourage the growth of a larger crystal.
Question
What is 'water of crystallisation'?
Answer
The fixed number of water molecules that enter into a loose chemical combination with a substance during crystallisation.
Question
Substances that contain a fixed number of water molecules in chemical combination are called _____ substances.
Answer
Hydrated.
Question
What is the chemical formula for Blue Vitriol?
Answer
$CuSO_{4} \cdot 5H_{2}O$.
Question
What colour change occurs when hydrated copper [II] sulphate is heated to become anhydrous?
Answer
It changes from blue to white.
Question
Term: Efflorescence
Answer
Definition: The phenomenon where crystalline hydrated salts lose their moisture to the atmosphere on exposure and turn into an amorphous powder.
Question
Give an example of an efflorescent substance.
Answer
Washing soda ($Na_{2}CO_{3} \cdot 10H_{2}O$).
Question
Term: Deliquescence
Answer
Definition: The phenomenon where water-soluble salts absorb moisture from the atmosphere to dissolve and change into a liquid state.
Question
Identify a common deliquescent crystal often used in laboratories.
Answer
Ferric chloride ($FeCl_{3}$).
Question
Why does common salt ($NaCl$) become sticky during the rainy season?
Answer
It contains deliquescent impurities like magnesium chloride ($MgCl_{2}$).
Question
What is the primary difference between hygroscopic and deliquescent substances?
Answer
Hygroscopic substances absorb moisture without changing their physical state, while deliquescent ones dissolve in the absorbed moisture.
Question
Term: Dehydrating Agent
Answer
Definition: A substance that removes chemically combined water or elements of water from compounds due to its strong affinity for it.
Question
Which acid acts as both a hygroscopic drying agent and a powerful dehydrating agent?
Answer
Concentrated sulphuric acid ($H_{2}SO_{4}$).
Question
What products are formed when concentrated $H_{2}SO_{4}$ reacts with glucose ($C_{6}H_{12}O_{6}$)?
Answer
Carbon (char) and water ($H_{2}O$).
Question
Water that does not lather readily with ordinary soap is defined as _____ water.
Answer
Hard.
Question
Which two metallic salts are the primary causes of water hardness?
Answer
Calcium and magnesium salts.
Question
What specific compounds cause temporary hardness in water?
Answer
Calcium bicarbonate ($Ca(HCO_{3})_{2}$) and magnesium bicarbonate ($Mg(HCO_{3})_{2}$).
Question
What specific compounds cause permanent hardness in water?
Answer
Chlorides and sulphates of calcium and magnesium ($CaCl_{2}, MgCl_{2}, CaSO_{4}, MgSO_{4}$).
Question
By what simple physical process can temporary hardness be removed?
Answer
Boiling.
Question
When temporary hard water is boiled, what insoluble precipitate is formed from calcium bicarbonate?
Answer
Calcium carbonate ($CaCO_{3}$).
Question
Which chemical is added to remove both temporary and permanent hardness from water?
Answer
Washing soda ($Na_{2}CO_{3}$).
Question
What is 'boiler scale'?
Answer
A crusty deposit formed in boilers due to the use of hard water, which wastes fuel and can be dangerous.
Question
What is potable water?
Answer
Water that is fit for human consumption and drinking purposes.
Question
What is the purpose of chlorination in water treatment?
Answer
To kill harmful germs and micro-organisms.
Question
Which substance is added to water to act as a coagulant for removing suspended mud or clay particles?
Answer
Alum (Potassium aluminium sulphate).
Question
What is the purpose of defluoridation in making water potable?
Answer
To reduce excess fluoride concentration to safe levels to prevent dental damage.
Question
Which common waterborne disease is caused by E. coli bacteria?
Answer
Diarrhoea.
Question
Anhydrous calcium chloride is often used in a _____ to keep other substances dry.
Answer
Desiccator.
Question
How does pressure on the surface of water affect its boiling point and freezing point?
Answer
Increased pressure increases the boiling point and decreases the freezing point.
Question
Which hydrated salt is known as Glauber's salt?
Answer
$Na_{2}SO_{4} \cdot 10H_{2}O$.
Question
Which hydrated salt is known as Epsom salt?
Answer
$MgSO_{4} \cdot 7H_{2}O$.
Question
What is the common name for $FeSO_{4} \cdot 7H_{2}O$?
Answer
Green vitriol.
Question
If the vapour pressure of a hydrated crystal exceeds atmospheric humidity, what phenomenon occurs?
Answer
Efflorescence.
Question
True or False: All hygroscopic substances are also drying agents.
Answer
True (Most hygroscopic substances are used as drying agents).
Question
In the context of mixtures, what is the role of a semi-permeable membrane?
Answer
It allows particles of a true solution to pass through but blocks those of colloids and suspensions.
Question
What happens to the solubility of oxygen in water as the temperature increases?
Answer
It decreases.
Question
Why is rain water considered soft water?
Answer
It does not contain dissolved calcium and magnesium salts that cause hardness.