ExamKrackers Chemistry Lecture 1 Exam #17?!

[MedGrl@2022]

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I am unable to figure out and understand the solution for EK Lecture 1 Exam Question #17.

17. What is the molecular weight of the gas?

A. 13 g/mol
B. 26 g/mol
C. 32 g/mol
D. 60 g/mol

EK answer: B is correct. The molarity of O2 is equal to the molarity of the welding gas of any other ideal gas at the same temperature and pressure.Is this an ideal gas law? How am I supposed to know this? Density divided by molecular weight is molarity. Therefore, we can set the ratios of density to molecular weight for oxygen and the welding gas equal to each other. We get: 1.3/32=1.1/M.W. How does this help me find the molecular weight? Isn't 1.1 the Molarity of the welding gas?

Thank you for your help!

Verónica

 

[Saint Fu]

Not sure about that particular explanation, but I wanted to point out that, given the answer of question #16, B is the only possible answer. A is the molecular weight of the empirical formula, CH, which is a compound that doesn't exist. B would correspond to C2H2, which would be acetylene. C and D are simply impossible to get with any compound with CH as the empirical formula.