Rank the following acids according to acid strength, strongest to weakest: HF, HCl, HBr. Explain your reasoning.

Answer: HBr, HCl, HF
Firstly, we must understand what is meant by "acid strength". Simply put, it's the concentration of "free" hydrogen ions (H+) in solution. Acids dissociate (liberate "free" hydrogen ions) when the X-H bonds break (X can be F, Cl, Br). It makes sense to assume that the weaker the X-H bond is, the more likely it's going to break and therefore liberate more hydrogen ions.
When we look at the periodic table, we can make two observations. 1) Going down the period, the electronegativity of the halogens (F, Cl, Br) in group VII decreases. The more electronegative the halogen, the bigger is the "pull"on the partially positively charged hydrogen. So, less electronegative halogens will have a weaker "pull" on the hydrogen (weaker bond).2) Going down the period, the atomic size of the halogens increase. The bigger the halogen atom, the longer the X-H bond must be. Longer bonds are weaker.

EK
Answered by Edgar K. Chemistry tutor

3566 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

Calculate the pH of the solution formed when 30 cm3 of 0.150 moldm-3 aqueous sulfuric acid is added to 30 cm3 of 0.200 moldm-3 aqueous potassium hydroxide at 25 C.


State and explain how the attraction between nuclei and outermost electrons varies across group 3 (2 marks)


Flask Q (volume = 1.00 x 103 cm3 ) is filled with ammonia (NH3) at 102 kPa and 300 K. Calculate the mass of ammonia in flask Q. (Gas constant R = 8.31 J K−1 mol−1 )


What are the strongest intermolecular forces in CH4, NH3 and H2O? From this deduce which has the highest boiling point, giving reasoning.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences