Question

6- According to the definition of an acid and the definition of a base, will the pH increase, decrease, or remain the same when NaCl is added to pure water? Explain.

7- What is a hydrogen bond? Explain how a hydrogen bond forms.

8- What feature of a soap molecule gives it cleaning ability?

9- What ion is responsible for a) acidic properties and b) basic properties?

10- Explain why a pH of 7 indicates a neutral solution -why not some other number?

Answer 1

6. When NaCl adds to water there is no change in pH value because it has no acidic or basic properties as none of the ions is capable of hydrolyzing the other. NaCl in water is a neutral solution.

7. The chemical bond that results from an electrostatic attraction between a hydrogen and an electronegative atom is called as a hydrogen bond. Hydrogen bond is formed between Hydrogen and atoms like oxygen, nitrogen, halogens. Here, hydrogen atom acts as an electrically positive atom being deficient of electrons and the electronegative atom acts as an electrically negative atom being electron rich.

8. The sodium and potassium end of the chain is water loving i. e. Hydrophilic.this is the polar part. Another part of soap which is non polar is hydrophobic i. e. Water repelling. The polar part is soluble in water and the non-polar part is soluble in oil. Our hands become dirty because of presence of oil which attracts dirt. Soap molecules attract the oils present and carry them when rinsed with water. This is how soap got it's cleaning ability.

9. H₃O⁺ ion is responsible for acidic properties and OH^- ion is responsible for basic properties.

10. The amount of H+ ions formed in pure water has pH equal to 7.As we know water is a neutral solution, so pH=7 is considered as the neutral point. At pH 7 the concentration of H+ ions is equal to the concentration of OH- ions.