Chapter 6, Problem 6STP

Interpretation Introduction

Interpretation: The compound needs to be identified.

Concept introduction: The molar mass is defined as mass of a substance in 1 mol. The number of units of the substance in 1 mol is $6.02\times {10}^{23}$ . This is Avogadro’s number and denoted by symbol $N_A$ .

Answer to Problem 6STP

Correct Answer: Option A. CO.

Explanation of Solution

The mass of a single molecule of the compound is $4.65\times {10}^{-23}\text{ g}$ . The number of molecules in 1 mol is $6.02\times {10}^{23}$ thus, mass of $6.02\times {10}^{23}$ molecules can be calculated as follows:

  $M=\left(6.02\times {10}^{23}{\text{ mol}}^{-1}\right)\left(4.65\times {10}^{-23}\text{ g}\right)=27.993\text{ g/mol}$

This is molar mass of the compound.

This corresponds to the compound CO because molar mass of CO is 28.01 g/mol. Therefore, option A is correct.

Conclusion

Since, the molar mass of H₂O is 18.015 g/mol, the molar mass of NO₂ is 46 g/mol and the molar mass of NH3 is 17.031 g/mol. Thus, options B, C and D are incorrect.