Acids

Acids are a group of chemical compounds which produces ______________ when dissolved in water

• hydroxide ions

• hydrogen ions

• proton

• hydrogen

What is the formula for Nitric Acid?

• HNO₂

• HNO₃

• HNO₄

• H₂NO₃

What is the formula for phosphoric acid?

• H₃PO₄

• H₂PO₄

• H₃P

• H₃PO₃

All acids have a pH value

• above 7

• around 7

• below 7

• exactly 7

Ethanoic acid is a weak acid because

(tick all that apply)

• it does not contain any hydrogen ions

• it has a very low pH

• it is used in cooking and flavouring food

• it is not fully ionised in water to form many hydrogen ions

• only one out of its 4 hydrogen atoms ionise in water

Answer explanation

Ethanoic acid has a pH of 3 or so (but below 7). This is not as low as strong aids with a pH of 1.

Although ethanoic acid is used in food, this is the consequence of it being a weak acid, not the cause.

Although only one out of its 4 hydrogen atoms ionises in water, we consider the extent of ionisation of the molecule (i.e. do all the acid molecules become ions?), not whether how many of the hydrogen atoms in the molecule form ions

Acids have a ___________ taste and also turn __________ litmus paper __________.

• sour, red, blue

• bitter, red, blue

• sour, blue, red

• bitter, green, red

Why are acids good conductors of electricity?

• Sike! They are not

• They have mobile ions

• They have mobile electrons

• They have mobile atoms

Answer explanation

Acids ionize in water. Hence, the ions can move freely act as mobile charge carriers

Strong and weak acids have similar electrical conductivities. True or false?

• True, as they both ionize in water and have mobile ions

• False, as one type of acid has more mobile ions and hence is a better electrical conductor

Answer explanation

Strong acids have much larger concentrations of mobile ions, so they will be better electrical conductors

Acids react with __________________ to form a salt and a gas which extinguishes with a 'pop' sound.

• alkalis

• bases

• carbonates

• reactive metals

Acids react with carbonates and hydrogen carbonates to form

• salt, water

• salt, water and carbon dioxide

• salt, carbonate

• salt, water and hydrogen

Answer explanation

Hydrogencarbonates are compounds containing the anion HCO3^-. An example is NaHCO3. They behave similarly to carbonates.