Q&A -Ask Doubts and Get AnswersPrevious Next
Atoms and Molecules
Q.6: Calculate the molar mass of the following substances.
(a) Ethyne, C2H2
(b) Sulphur molecule, S8
(c) Phosphorus molecule, P4 (Atomic mass of phosphorus = 31)
(d) Hydrochloric acid, HCl
(e) Nitric acid, HNO3
(a) The ethyne (C2H2 ) contains carbon and hydrogen atoms. The gram atomic mass of carbon is 12 g and hydrogen is 1 g.
So, Molar mass of C2H2 = 2(Atomic mass of C) +2(Atomic mass of H)
= 2(12g) + 2(1g) = 26g
Therefore, molar mass of ethyne is 26g.
(b) The octasulphur molecule(S8 ) contains eight sulphur atoms. The gram atomic mass of sulphur is 32 g.
So, Molar mass of S8 = 8(Atomic mass of S)
= 8 (32g) = 256g
Therefore, molar mass of octasulphur molecule is 256g.
(c) The tetraphosphorus (P4 ) contains four phosphorus atoms. The gram atomic mass of phosphorus is 31 g.
Molar mass of P4 = 4(Atomic mass of P)
= 4 (31g) = 124g
Therefore, molar mass of tetraphosphorus molecule is 124g.
(d) The hydrogen chloride (HCl ) contains chlorine and hydrogen atoms. The gram atomic mass of chlorine is 35.5 g and hydrogen is 1 g.
So, Molar mass of HCl = Atomic mass of H +Atomic mass of Cl
= 1g + 35.5g = 36.5g
Therefore, the molar mass of hydrogen chloride is 36.5g.
(e) The nitric acid(HNO3 ) contains hydrogen, nitrogen, and oxygen atoms. The gram atomic mass of nitrogen is 14 g, oxygen is 16 g and hydrogen is 1 g.
So, Molar mass of HNO3 = Atomic mass of H + Atomic mass of N + 3(Atomic mass of O)
= 1g + 14g + 3(16g) = 63g
Therefore, the molar mass of nitric acid is 63g.
Related Questions for Study
What our students and parents say about us!
Saiyam is using EduSaksham online courses from past one year. He is able to complete his tutorials, worksheets, and assignments on his own. Once he is done with worksheets, he can check his answers and if he has done any mistakes, then he can check the correct answers and explanations. They have been given so well that he is able to understand them himself and rarely he asks us for any clarification. He enjoys using the platform and has learned and improved a lot in Mathematics. I would recommend EduSaksham to all parents who want their kids to learn in a structured way and also enjoy the learning process.
Neeraj (Saiyam's Father)
I would like to thank Edusaksham on behalf of my son Aditya who attended " Math Olympiad crash course for 5 weeks". As per Aditya, this course helped him to understand new topics like Roman numerals and decimal places which were not taught in his school till date and had a better understanding of other topics. I personally thank EduSaksham for all the help and support.
Geeta Bansal (Aditya's Mother)
We had a good experience with EduSaksham. Because sheets are available online, Vedant enjoyed doing more and more sheets without any reminders. I could leave him on his own as he was very much motivated to cover the topics. Practice is very important in maths but it becomes difficult for us to prepare sheets, I am glad we found EduSaksham where in a lot of in a lot of sheets are available for practice and the quality of questions are also good. As it's a venture from IITians we could think of giving it a try and I am glad we tried
Shikha Chowdhary (Vedant's Mother)
I have grown up in a family where my father used to give me practice maths paper every day which I need to finish before I go to play. I think that strong foundation of solving new questions every day helped me to clear my IITJEE exam. But as working women, I always had time challenge to create practice Math papers for my daughter. Thanks to EduSaksham, their questions are so logical and conceptual that I don't feel the guilt of not creating practice questions by myself :). There are plenty of worksheet along with the tutorials for each chapter. It has made parents life easier :) And the best part is my daughter loves doing it. Thank you EduSaksham.