ACIDS, BASES & OXIDES (CHEM)

secondary 3 syallbus

what is an acid

An acid is a substance that produces hydrogen ions (H⁺) in aqueous solutions.

What kind of taste do acid’s have

A sour taste

all acids have ____ ions?

hydrogen (H⁺)

when acids ____ in water, acid molecules ____ to produce Hydrogen ions

(dissolve) and (ionize)

In which state does a acid produce hydrogen ions

only in an aqueous state

what pH is an acid?

lower than 7

what are the change of colours(the indicators: litmus paper + universal indicator + methyl orange)

Acids turn litmus paper from blue to red and Universal indicators from green to red/orange/yellow and Methyl orange from orange to red and universal indicator (when alkaline turns from green to blue/violet) (when acidic turns from green to red/orange/yellow) (orange to yellow for alkaline in methyl orange)

Acids react with ___ ____ to form a s___ and h______ g___

reactive metals, salt, hydrogen gas (metal + acid —> salt + hydrogen gas)

How can we test for hydrogen gas?

Hydrogen gas can be tested by using a lit splint at the mouth of the test tube. If hydrogen is present, it would extinguish the lit splint with a "pop" sound.

Which metals do not react with acids

Metals like gold, silver, and platinum do not react with acids due to their high stability and lack of reactivity.

Acids react with b_____

bases

what occurs with an acid reacts with a base to form salt and water

This process is known as neutralization, where the acid and base react to produce a salt and water as products.

Acids react with C___________

Carbonates

A liquid T has a sour taste and it turns blue litmus paper red. Describe 2 different chemical tests and the results of each test to confirm that T is an acid

One test is the reaction of liquid T with a metal carbonate, such as calcium carbonate, which produces carbon dioxide gas, indicated by bubbling.

another test is….

Test: Measure the pH of liquid T using universal indicator paper or solution.

• Result: The indicator turns red/orange/yellow

• Conclusion: This shows that the pH is low (below 7), confirming that T is acidic.

Explain why solid citric acid does not conduct electricity but a solution of citric acid in water does

Solid citric acid consists of neutral molecules that do not have free-moving ions, therefore it cannot conduct electricity. However, when dissolved in water, citric acid dissociates into ions, which allows the solution to conduct electricity.

Suggest why barium reacts with dilute hydrochloric acid but does not appear to react with dilute sulfuric acid

Barium reacts with dilute hydrochloric acid because it can displace hydrogen ions in the reaction, producing barium chloride and hydrogen gas. In contrast, barium does not react with dilute sulfuric acid because barium sulfate is insoluble and forms a precipitate, preventing further reaction.

Write the ionic equation between a) magnesium and hydrochloric acid b) calcium carbonate and nitric acid

a) Mg + 2HCl → MgCl₂ + H₂
b) CaCO₃ + 2HNO₃ → Ca(NO₃)₂ + CO₂ + H₂O

What is a strong acid?

a strong acid is one that is completely ionized in an aqueous solution

What is a weak acid?

A weak acid is one that only partially ionizes in an aqueous solution.

Difference in pH value using a pH meter

A strong acid contains more hydrogen ions (H⁺), thus has a lower pH than a weak acid of the same concentration.

pH is calculated based on the ______ present per unit volume in a solution

concentration of hydrogen ions (H⁺)

strong acids contains ______, thus turns universal indicator from green to red.

more hydrogen ions (H⁺)

strong acid contains_______, thus has a higher conductivity than weak acid.

more free ions

Weak acids turns________ from green to yellow/orange.

universal indicator

concentration meaning

refer to the number of the acid molecules dissolved in a given volume of water (can be changed)

strength meaning

refer to the degree of ionisation in water (how acid seperate into ions) cannot be changed

how is a strong acid different from a weak acid?

Aspect	Strong Acid	Weak Acid
Ionization in water	Completely ionizes (100%)	Partially ionizes (less than 100%)
Concentration of H⁺	High concentration of hydrogen ions (H⁺)	Lower concentration of hydrogen ions (H⁺)
pH	Lower pH (around 1-3)	Higher pH (around 4-6)
Conductivity	High (due to more free ions)	Lower (fewer ions in solution)
Example	Hydrochloric acid (HCl)	Ethanoic acid (CH₃COOH)

name a strong acid. name a weak acid

• Strong acid: Hydrochloric acid (HCl)

• Weak acid: Ethanoic acid (also called acetic acid, CH₃COOH)