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Experiment 1: Determination of the Formula Unit

SK015 Chemistry Lab Manual

Objectives

  • Synthesise a zinc chloride compound.
  • Determine the empirical formula of zinc chloride.

Introduction

A quantitative analysis can be used to determine the composition of an unknown compound. In this experiment, a compound composed of zinc and chlorine will be prepared. By measuring the masses of the reactants and products, the mole ratio and percentage composition can be deduced to identify the formula unit.

Requirements

Reagents

  • 6 M HCl Solution
  • Zinc Powder

Apparatus

  • Analytical Balance
  • Hot Plate
  • Crucible & Cover

Procedure & Data Recording

Step 3 of 4
1

Weigh the crucible and approximately 0.25g of Zinc powder.

2

Add 10 mL of 6 M HCl. Heat slowly until completely dry.

CAUTION: Carry out this step in a fume cupboard. Avoid overheating to prevent product melting.
3

Cool down. Reheat until mass difference is ≤ 0.02 g (Constant Mass).

Quantitative Analysis Results

Review your data before submission.

Data Summary

1. Mass of empty crucible: 0.0000 g
2. Mass of crucible + zinc: 0.0000 g
3. Mass of zinc powder: 0.0000 g
1st Heat 2nd Heat 3rd Heat
— — —
5. Mass of zinc chloride: 0.0000 g
6. Mass of chlorine: 0.0000 g

Formula Deduction

Mol Zn

0.0000

Mol Cl

0.0000

Simplest Ratio Zn:Cl ≈ 1 : 2

Empirical Formula

ZnCl₂

Notification

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