Question

1. note the mass of a copper(i) oxide formula unit in the image below. what is the mass of 8.250 moles of cu₂o?

17.34 u
17.34 g
1,181 u
1,181 g

1. what is the mass of 8.12 × 10²³ molecules of co₂ gas? (atomic mass of carbon = 12.011 u, oxygen = 15.999 u.)

32.6 g
44.0 g
48.9 g
59.3 g

Explanation:

Step1: Calculate molar mass of \(Cu_2O\)

From the image, the formula unit mass of \(Cu_2O\) is \(143.091\space u\). Since \(1\space mol\) of a substance has a mass (in grams) equal to its formula unit mass (in \(u\)), the molar mass \(M\) of \(Cu_2O\) is \(M = 143.091\space g/mol\)

Step2: Use the formula \(m=n\times M\)

Given \(n = 8.250\space mol\) (number of moles) and \(M=143.091\space g/mol\) (molar mass). Then \(m=8.250\times143.091\)

$$m = 8.250\times143.091=1181.40075\approx1181\space g$$

Answer:

\(1181\space g\)