Abottle of water has a label
saying 'suitable for chemical
analysis'. describe how this
water has been produced.
explain how you would check
to see if this water really is
suitable for analysis.

The said water is purified by means of either one of the processes like double distillation, reverse osmosis, deionization or more than one of them.

In chemical analysis of a chemical substance, the water used is needed to be free from any sort of chemical ions that are generally present in tap water. These ions if present may interfere in the chemical reactions in which water is used as a solvent, or can interfere with the values of estimation of a particular ion.

So the water is either distilled for two times to get rid of any types of ions dissolved in it. Or it can be purified by means of reverse osmosis through a semipermiable membrane. Or it can be deionized by means of using electrolysis at particular voltages. More than one processes can be done to get higher percentages of purification.

the dependant variable is spilled water

the independent is the heat

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.