What is a chemical reaction?
A process breaking and forming bonds to produce new substances.
What indicates a chemical reaction may have occurred?
Gas evolution, colour change, temperature change, light emission, or precipitate formation.
How are chemical reactions classified?
By how atoms or ions rearrange and bind together.
What are direct combination reactions?
Reactions where two or more substances combine to form a new compound.
How does magnesium react when heated in oxygen?
It burns with a bright white flame forming white magnesium oxide.
Why is a direct combination reaction?
Because two substances combine to form a new compound.
What are decomposition reactions?
Reactions where a compound breaks into simpler components using energy like heat or light.
What happens to some metal oxides when heated?
They decompose into the metal and release oxygen gas.
What does red mercury oxide decompose into on heating?
Silver-coloured liquid mercury and colourless oxygen gas.
What are the products when calcium carbonate decomposes on heating?
Calcium oxide and colourless carbon dioxide gas.
What effect does the oxygen gas from red mercury oxide decomposition have on a lighted matchstick?
It increases the glow of the matchstick.
What defines single replacement reactions?
An element replaces another element in one of its compounds.
What types of replacements occur in single replacement reactions?
Replacement of hydrogen in acids or water by metals and replacement of metals in salt solutions by other metals.
Which metals react with dilute hydrochloric acid to produce hydrogen gas?
Magnesium, zinc, and iron react to form hydrogen gas.
How does copper react with dilute hydrochloric acid?
Copper does not react and produces no gas under these conditions.
What is the order of reaction rates with dilute hydrochloric acid?
Magnesium reacts fastest, then zinc, then iron.
What does a highly reactive metal like sodium produce when it replaces hydrogen in cold water?
A metal hydroxide and hydrogen gas.
How does sodium react with cold water?
Instantly and vigorously, forming sodium hydroxide, hydrogen gas, and heat.
What happens when zinc is placed in copper sulphate solution?
Zinc replaces copper, producing colourless zinc sulphate and red copper deposits.
What is the chemical reactivity series?
An arrangement of metals in descending order of chemical reactivity.
Which metal is most reactive in the chemical reactivity series?
Potassium is the most reactive metal.
Which metal is least reactive in the chemical reactivity series?
Gold is the least reactive metal.
What happens when metals above hydrogen react with dilute acids?
They replace hydrogen in dilute acids.
Can metals below hydrogen replace hydrogen in dilute acids?
No, metals below hydrogen cannot replace hydrogen.
What can a metal earlier in the reactivity series do to a later metal's salt solution?
It can replace the later metal from its salt solution.
Why might aluminum not react instantly with dilute acids despite its position?
An aluminum oxide layer prevents acid from reaching the metal initially.
What happens in double replacement reactions?
Cations and anions of two ionic compounds exchange positions to form two new compounds.
What ions make up an ionic compound?
A positive cation and a negative anion.
What are the three types of double replacement reactions?
Acid with alkali, acid with salt, and one salt solution with another salt solution.
What is a neutralization reaction?
An acid reacts with an alkali to form a salt and water.
What defines a precipitation reaction?
Two salt solutions react to form a new substance that does not dissolve in water.
What color does universal indicator turn in an acidic medium?
Red.
What are the products when hydrochloric acid reacts with sodium hydroxide?
Sodium chloride and water.
What precipitate forms when sodium chloride solution reacts with silver nitrate solution?
A white precipitate of silver chloride.
What color is universal indicator in a strong alkali like sodium hydroxide?
Violet
What color does universal indicator show in a neutral solution like sodium chloride?
Green
What color does universal indicator show in a strong acid like hydrochloric acid?
Red
What gas is released when hydrochloric acid reacts with sodium carbonate?
Carbon dioxide
What happens to limewater when carbon dioxide is bubbled through it?
It turns turbid
What is a precipitation reaction?
A reaction between salt solutions producing an insoluble solid precipitate
What precipitate forms when silver nitrate reacts with sodium chloride?
White insoluble silver chloride
What is oxidation in terms of electrons?
Oxidation involves loss of one or more electrons.
What does reduction involve in terms of electrons?
Reduction involves gain of one or more electrons.
What does a reducing agent do in a chemical reaction?
It loses one or more electrons.
What does an oxidizing agent do in a chemical reaction?
It gains one or more electrons.
Why do oxidation and reduction occur simultaneously?
Because electrons lost in oxidation are gained in reduction.
Why do most metals act as reducing agents?
Because they tend to lose electrons.
What is the oxidation half-reaction of magnesium?
In , which acts as the reducing agent?
Zinc acts as the reducing agent.
What can a more reactive metal do in a salt solution of a less reactive metal?
It can replace the less reactive metal from its salt solution.
What are the products when sodium reacts with water?
Sodium hydroxide and hydrogen gas are formed.
What forms when magnesium reacts with dilute hydrochloric acid?
Magnesium chloride and hydrogen gas are formed.
What does hard water contain that causes deposits in pipes?
High percentages of calcium and magnesium salts.
How do precipitation reactions treat hard water?
By removing dissolved calcium and magnesium salts as insoluble precipitates.
What are the products when red mercury oxide is heated?
Silver-coloured mercury and oxygen gas are produced.
In the reaction , what happens to magnesium?
Magnesium loses electrons.
In the reaction , what happens to hydrogen ions?
Hydrogen ions gain electrons.
Test your knowledge with 29 questions on Types of Chemical Reactions.
1. What distinguishes a chemical reaction from a physical change?
2. Which observation provides evidence that a chemical reaction may have occurred?
Review the complete course in the study sheet for Types of Chemical Reactions.
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