+1 vote
in Chemistry by (29.7k points)

(i) What do the following symbols / formulae stand for: 

(a) 2O      (b) O     (c) O3       (d) H2

(ii) Give the chemical formula of the following compounds: 

(a) Potassium carbonate (b) Calcium chloride 

(iii) Calculate the formula unit mass of Al2(SO4)3

(Given: Atomic mass of Al = 27 u, S = 32 u, O = 16 u) 

2 Answers

+2 votes
by (127k points)
selected by
Best answer

(i) (a) 2O = 2 atoms of oxygen 

(b) O2 = Diatomic oxygen 

(c) O3 = Triatomic oxygen / ozone 

(d) H2O=Two atoms of hydrogen and one atom of oxygen construct one molecule of water (H2O) 

(ii) Potassium carbonate - K2CO

Calcium chloride - CaCl

(iii) Formula unit mass of any compound is the sum of atomic masses of all atoms in the formula of that compound. 

Formula unit mass of Al2(SO4)3 

Atomic mass of Al = 27 × 2 = 54 u 

Atomic mass of S = 32 × 3 = 96 u 

Atomic mass of O = 16 × 12 = 192 u 

Formula unit mass = 54 + 96 + 192 = 342 u. 

Hence, Formula unit mass of Al2(SO4)3 is 342.

0 votes
by (667 points)

2O represent 2 separate atom while O2 represent 1 molecules of oxygen gas containing 2 atoms

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.