Question

for each statement below, indicate whether it is true or false. 1. breaking the hydrogen bond between two water molecules is called dissociation. (click to select) 2. when water dissociates, an oxygen atom separates from the rest of the molecule. (click to select) 3. the hydroxide ion has an overall charge of (-1). (click to select) 4. a hydrogen ion is the same as a proton. (click to select) 5. when a hydrogen ion separates from a water molecule, it usually combines with another water molecule to form a hydronium ion. (click to select) 6. a hydronium ion has the formula (ce{h_{2}o^{+}}). (click to select) 7. in pure water, at (25^circ \text{c}), about (10%) of the water molecules are dissociated at any given time. (click to select) 8. in pure water, the concentration of hydrogen ions always equals the concentration of hydroxide ions. (click to select) 9. in pure water, the concentration of hydrogen ions is (1 \times 10^{-7}) molar. (click to select) 10. water dissociates into oppositely charged ions. (click to select)

Explanation:

1. Water dissociation refers to the splitting of a single water molecule into ions, not breaking hydrogen bonds between two water molecules.
2. Water dissociation is the separation of an H⁺ (hydrogen ion) from the H₂O molecule, leaving OH⁻ (hydroxide ion).
3. The hydroxide ion is formed when H₂O loses an H⁺, resulting in an overall charge of -1.
4. A hydrogen ion (H⁺) is a single proton, as the hydrogen atom's nucleus is just a proton with no electrons.
5. When H⁺ separates from H₂O, it bonds to another H₂O molecule to form H₃O⁺ (hydronium ion).
6. The correct formula for a hydronium ion is H₃O⁺, not H₂O⁺.
7. At 25°C, only a tiny fraction (≈1 in 10⁷, or 0.00001%) of water molecules are dissociated, not 10%.
8. Pure water is neutral, so the concentrations of H⁺ and OH⁻ are always equal.
9. At 25°C, the ion product of water $K_w = [H^+][OH^-] = 1 \times 10^{-14}$, so $[H^+] = 1 \times 10^{-7}$ molar.
10. Water dissociates into H⁺ (positive) and OH⁻ (negative), which are oppositely charged ions.

Answer:

1. False
2. True
3. True
4. True
5. True
6. False
7. False
8. True
9. True
10. True