School of Nursing and Academic Division of Midwifery

RLO: Acids, Alkalis & Bases: An Introduction

Alkaline Solutions

The definition of an alkali is: “A substance with free hydroxide ions (OH^-) in solution”.

Move the bars on the bar chart (on the right) to illustrate the difference in OH^- and H⁺ ratios in an alkaline solution.

Now, on the pH scale, drag the arrow to indicate the range for alkalis.

Remember: The pH scale indirectly measures the concentration of H⁺ ions in solution. Because alkalis have more OH^- than H⁺ ions, their relative concentration of H⁺ is low and so the pH value will be high.

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