15.5
강산 및 염기 용액
View the full transcript and gain access to JoVE Core videos
Q1: Why does a strong acid produce hydronium ions equal to its initial concentration?
Strong acids dissociate completely in water, meaning every acid molecule breaks apart into hydronium ions and anions. Since the hydronium ions from water's autoionization are negligible, the hydronium ion concentration equals the acid's starting concentration. For example, a 0.10 molar HCl solution produces 0.10 molar hydronium ions.
Q2: How do you calculate pH from the hydronium ion concentration of a strong acid?
pH is calculated using the negative logarithm of the hydronium ion concentration: pH = -log[H+]. For a 0.10 molar HCl solution with 0.10 molar hydronium ions, pH = -log(0.10) = 1. Conversely, if pH is known, you can find hydronium concentration by taking the antilog of the negative pH value.
Q3: What is the difference between Group 1 and Group 2 metal hydroxides as strong bases?
Group 1 metal hydroxides like sodium hydroxide produce one mole of hydroxide ions per mole of base. Group 2 metal hydroxides like calcium hydroxide produce two moles of hydroxide ions per mole of base. For example, 0.020 molar calcium hydroxide generates 0.040 molar hydroxide ions, making it more basic than Group 1 hydroxides at the same concentration.
Q4: How do ionic metal oxides function as strong bases in aqueous solution?
Ionic metal oxides like sodium oxide and calcium oxide are strong bases because their oxide ions react with water to produce hydroxide ions. This reaction generates OH- ions that increase the solution's basicity. The resulting hydroxide ion concentration can then be used to calculate pOH and pH values.
Q5: How can you determine hydroxide ion concentration from pOH?
Hydroxide ion concentration is found using the equation pOH = -log[OH-]. If pOH is known, rearrange to solve for [OH-] by multiplying both sides by negative one and taking the antilog. For example, a solution with pOH 4.30 has a hydroxide ion concentration of 5 × 10⁻⁵ molar.
Q6: What is the relationship between pH and pOH in aqueous solutions?
pH and pOH are related by the equation pH + pOH = 14 at 25°C. This relationship allows you to calculate one value if you know the other. For instance, if a strong base solution has pOH 4.30, its pH is 9.7, indicating a basic solution with low hydronium ion concentration.
Q7: How do molar ratios help determine ion concentrations in strong acid and base solutions?
Molar ratios from the dissociation equation show how many ions form per molecule of acid or base. Since strong acids and bases dissociate completely, these ratios directly give ion concentrations. For example, 0.030 molar HCl produces 0.030 molar hydronium ions using a 1:1 ratio, while 0.015 molar Ba(OH)2 produces 0.030 molar hydroxide ions using a 1:2 ratio.