7. (a) Define (i) acid, (ii) base, according to the theory of Arrhenius, who is pictured on the right - Leaving Cert Chemistry - Question 7 - 2013

A base is defined as a substance that dissociates to give hydroxide ions (OH⁻) in aqueous solution.

Neutralisation is the chemical reaction between an acid and a base, resulting in the formation of salt and water. It is characterized by the equation:

The strong acid that is a constituent of gastric juice is hydrochloric acid, with the formula HCl.

To measure the concentration of suspended solids, follow these steps:

1. Find the mass of a dry filter paper using a balance.
2. Filter a known volume of the water sample through the weighed filter paper.
3. Dry the filter paper completely.
4. Reweigh the filter paper to determine the mass after filtering.
5. Calculate the mass of suspended solids by subtracting the initial weight of the filter paper from the final weight.

To measure the concentration of dissolved solids, perform the following:

1. Find the mass of an evaporating dish using a balance.
2. Evaporate a known volume of the filtered water in the dish until dry.
3. Allow the dish to cool and then reweigh it.
4. Calculate the mass of dissolved solids by subtracting the initial weight of the dish from the final weight.

To express the concentration of suspended solids in grams per litre: $0.015 ext{ g} ext{ in } 0.1 ext{ L} = 0.15 ext{ g/L}$ Thus, the concentration is 0.15 g/L.

To express the concentration in parts per million (ppm): To convert grams to mg, we multiply by 1000:

• For suspended solids: $0.015 ext{ g} = 15 ext{ mg}$
• For dissolved solids: $0.17 ext{ g} = 170 ext{ mg}$

Now, using the total volume of the sample: ext{ppm} = rac{ ext{mg of substance}}{ ext{L of solution}} \times 1000

Thus,

• Concentration of suspended solids in ppm: $15 ext{ ppm}$
• Concentration of dissolved solids in ppm: $170 ext{ ppm}$