3.15: explain why, if soluble salts are prepared from an acid and an insoluble reactant:
a) excess of the reactant is added
b) the excess reactant is removed
c) the solution remaining is only salt and water

3.16: explain why, is soluble salts are prepared from an acid and a soluble reactant:
a) titration must be used
b) the acid and the soluble reactant are then mixed in the correct proportions
c) the solution remaining, after reaction, is only salt and water.

these are two points in the gcse specification i do not completely understand. can anyone ?

Soluble salts can be made by reacting acids with either soluble or insoluble bases.

answer: option (4) is the correct answer.

explanation:

areas which are at low altitudes and near the equator tend to receive direct sunlight from the sun. hence, heat energy or radiations from the sun make these areas warmer and they have warmest water.

whereas areas which are at high altitudes and away from the equator do no receive direct sunlight. hence, no direct contact from the sun makes these regions colder and thus, they have colder water.

thus, we can conclude that the statement areas at low latitudes near the equator have the warmest water because they receive the most direct sunlight best explains the relationship between an area's geography and the temperature of its surface water.