Question

what is the total number of moles contained in 115 grams of c₂h₅oh?
a. 1.00 b. 1.50 c. 3.00 d. 2.50
c = 12.1 * 2
h = 1 * 5 + 1
o = 16
= 46.2
\frac{115}{46.2} = 2.48 \approx 2.5

Explanation:

Step1: Calculate molar mass of \(C_2H_5OH\)

Molar mass of \(C\): \(12.01\ g/mol\), there are \(2\) \(C\) atoms. Molar mass of \(H\): \(1.008\ g/mol\), there are \(6\) \(H\) atoms (\(5 + 1\)). Molar mass of \(O\): \(16.00\ g/mol\).
Molar mass \(M=(2\times12.01)+(6\times1.008)+16.00\)
\(M = 24.02+6.048 + 16.00=46.068\ g/mol\approx46\ g/mol\)

Step2: Calculate number of moles

Use the formula \(n=\frac{m}{M}\), where \(m = 115\ g\) (mass) and \(M\approx46\ g/mol\) (molar mass)
\(n=\frac{115\ g}{46\ g/mol}=2.5\ mol\)

Answer:

D. 2.50