Unit 19 Chemical Reactions & bonding

What is an acid defined as?

A corrosive substance which has a pH lower than 7, caused by a high concentration of hydrogen ions.

What is activation energy?

The minimum amount of energy that colliding particles must have for them to react.

What is an alkali?

A base which is soluble in water, producing more hydroxide ions than hydrogen ions when dissolved in water, with a pH greater than 7.

Define a base.

A substance that reacts with an acid to neutralise it and produce a salt.

What does 'corrosive' mean in chemistry?

Able to damage metal, stonework, clothes, and skin; strong acids and alkalis are corrosive.

Describe a displacement reaction.

A reaction that occurs when a more reactive element replaces a less reactive element in a compound.

What is an endothermic reaction?

A reaction in which energy is taken in.

What is an exothermic reaction?

A reaction in which energy is given out to the surroundings, causing the temperature to increase.

What is an indicator used for?

A substance that has different colors, depending upon the pH of the solution it is in.

How does litmus paper react to acids and alkalis?

Red litmus turns blue in alkalis, while blue litmus turns red in acids.

What does it mean if a substance is neutral?

When a substance is neither acidic nor alkaline, and has a pH of 7.

What is neutralization?

The reaction between an acid and a base to form a salt plus water.

Define oxidation.

The gain of oxygen, or loss of electrons, by a substance during a chemical reaction.

What does pH measure?

Scale of acidity or alkalinity. A pH value below 7 is acidic, a pH value above 7 is alkaline.

What is a saturated solution?

A solution in which no more of the solute will dissolve.

What does 'soluble' mean?

Able to dissolve in solvent.

What is a solvent?

The liquid in which the solute dissolves to form a solution.

What is a solution?

When particles mixed with the river water are dissolved and carried in the water.

Describe thermal decomposition.

Type of reaction in which a compound breaks down to form two or more substances when it is heated.

How does universal indicator paper work?

Paper stained with universal indicator, a chemical solution that produces many different color changes corresponding to different pH levels[cite: 381].

What ions do acids produce in aqueous solutions?

Hydrogen ions (H+).

What ions do alkalis produce in aqueous solutions?

Hydroxide ions (OH−).

What is the pH value of acidic solutions?

Less than 7.

What is the pH value of alkaline solutions?

Greater than 7.

What is the pH value of a neutral solution?

7.

How can the pH of a solution be measured?

Using a pH probe, or estimated using universal indicator and a color chart.

What are the products when acids react with metals?

A salt and hydrogen.

Give an example of a reaction between hydrochloric acid and magnesium, including the word equation.

Hydrochloric acid + magnesium → magnesium chloride + hydrogen.

What type of salt does Sulfuric Acid (H2​SO4​) make?

Sulfates.

What type of salt does Hydrochloric Acid (HCl) make?

Chlorides.

What type of salt does Nitric Acid (HNO3​) make?

Nitrates.

What is a solute?

The substance that dissolves to make a solution.

What happens during dissolving?

Particles of solvent collide with particles of solute, surround them, and gradually move them away until they are evenly spread through the solvent.

What determines the ability of a solvent to dissolve a solute?

The type of bonding occurring inside (ionic, metal) or between (covalent) that solute.

What is the saying often used to describe solubility?

'Like dissolves like'.

What is solubility a measurement of?

How much of a substance will dissolve in a given volume of a liquid.

How is solubility shown in the provided table for solids?

As the grams of a solute per 100 g of water.

How does pressure affect the solubility of a gas in a solvent?

As the pressure increases, more gas molecules dissolve into the solvent.

How does temperature generally affect the solubility of gases?

Gases tend to become less soluble as the temperature of the solvent increases.

What are substances with high solubilities called?

Very soluble substances.

What is a precipitate?

An insoluble product that forms when two solutions are mixed and react together.

What is a precipitation reaction?

The reaction that produces a precipitate.

Why are state symbols important in balanced equations for precipitation reactions?

Without the (s) for solid, it would not be obvious that a precipitate has formed.

Which common salts are generally soluble?

All common sodium, potassium, and ammonium salts, and all nitrates.

Which common chlorides are insoluble?

Silver chloride and Lead chloride.

Which common sulfates are insoluble?

Lead sulfate, Barium sulfate, and Calcium sulfate.

Which common carbonates are soluble?

Sodium carbonate, potassium carbonate, and ammonium carbonate.

Which common hydroxides are soluble?

Sodium hydroxide, potassium hydroxide, and ammonium hydroxide.

Acid + Metal Carbonate -> Salt + Water + Carbon Dioxide (derived from objectives and