Pre-Lab 19A: Solubility Curve of KNO3

Purpose Solubility refers to the amount of solute that can be dissolved in a certain volume of solvent under certain conditions. In this experiment, you will be examining the relationship between temperature and the solubility of potassium nitrate (KNO3). The solvent will be water. Using class data, you will construct a solubility curve for KNO3.

Key Question What is a solubility curve?

Background Define: solution solute precipitate

Drawing Download or make a drawing of rock candy on a string

Section 2 You will be dissolving potassium nitrate into warm water Each lab station will have a different mass of KNO3: NOTE: change from book: each lab station increases solute by1.00 grams (accuracy to the 100th place: two decimals): lab 1 = 1.00 g lab 2 = 2.00 g lab 3 = 3.00 g etal…… Be certain you tare the mass pan Liquid volume must be exact and to an accuracy 0.1 ml You will heat, then cool the solution to form a precipitate This is a critical step: record the temperature (accuracy of 0.1 degrees C) at which you first see crystals gather at the bottom of the test tube

Clean up: Pour the solution into the trash Use a test tube brush and warm water to COMPLETELY clean the test tube Also, do not lick your fingers, why? KNO3 is a laxative!!!!

Section 3: SHOW YOUR WORK for part A you will be calculating water’s mass NOT MEASURING!! (density of water = ? ) Part B: use part A ratio = unknown ratio Record your solubility/temperature values on the data chart: NOTE: data chart must have 7 data columns Critical step: Your data MUST then be recorded on the chart on the white board Thus, the board’s data is the data you will use for making your solubility graph

Section 4: Make a solubility graph from the classes’ data Use graphing rules Add/change this to your lab: d. Explain why e. Show your work

Post Lab: