Beginner Topic 519 of 1102 Acids, Bases & Electrochemistry
Strong Acids
Acids that ionize completely in water, such as HCl, HBr, HI, HNO3, H2SO4 and HClO4.
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In-depth explanation of Strong Acids
Strong acids such as HCl, HBr, HI, HNO3, H2SO4 (for its first proton), HClO4 and HClO3 ionize essentially completely in water, so the hydrogen ion concentration equals the acid concentration. Their conjugate bases are so weak that they do not measurably recombine with protons. Because dissociation is complete, the pH of a strong acid solution is calculated directly from its formal concentration. Sulfuric acid needs more care because its second proton is only partly dissociated. Strong acids are widely used as titrants and reagents wherever a sharp and predictable acidity is required.
Going deeper: Strong Acids
Key ideas: The six common strong acids are HCl, HBr, HI, HNO3, H2SO4 (first proton) and HClO4. They ionize essentially completely, so [H+] equals the acid concentration times the number of fully ionizing protons. For 0.010 M HNO3 pH is 2.00. Only the first proton of H2SO4 is strong; the second has Ka about 0.012.
Common mistakes and connections: Mistakes: using an equilibrium table for a strong acid, doubling [H+] for H2SO4 without checking that HSO4- is only partly dissociated, and confusing strong with concentrated. Strength means degree of ionization, concentration means amount per volume. Water levels all stronger acids to H3O+.
Visualization of Strong Acids
A strong acid ionizes completely, so pH is simply the negative log of its concentration; 0.020 M HNO3 gives pH 1.70. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A 0.020 M HNO3 solution has [H+] = 0.020 M and pH 1.70.
Frequently asked questions about Strong Acids
What is Strong Acids?
Acids that ionize completely in water, such as HCl, HBr, HI, HNO3, H2SO4 and HClO4.
Is Strong Acids a beginner, intermediate or advanced topic?
Strong Acids is a beginner topic in Acids, Bases & Electrochemistry. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Strong Acids?
Study these earlier topics in Acids, Bases & Electrochemistry first: Autoionization of Water, pH Scale, pOH and pKw.
What comes after Strong Acids?
The next topics in Acids, Bases & Electrochemistry are Strong Bases and Weak Acids.
Can I practise Strong Acids with quizzes?
Yes. The interactive lesson includes a self-check question on Strong Acids, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where Strong Acids fits in Acids, Bases & Electrochemistry
Strong Acids is topic 9 of 105 in Acids, Bases & Electrochemistry.