Question

how would you calculate the molar mass of carbon dioxide (co₂)?
a. by subtracting the molar mass of oxygen from carbon
b. by adding the molar mass of carbon to twice the molar mass of oxygen
c. by calculating the density of co₂
d. by measuring the pressure of co₂ gas

Explanation:

Step1: Recall molar mass calculation rule

Molar mass of a compound is sum of molar masses of its elements. For \(CO_2\), there is 1 C atom and 2 O atoms.

Step2: Analyze each option

• Option a: Subtracting is wrong. Molar mass of compound is sum, not difference.
• Option b: Molar mass of \(CO_2 = M_{C}+ 2\times M_{O}\). This is correct as per molar mass calculation rule.
• Option c: Density is \(d=\frac{m}{V}\), not related to molar mass calculation directly.
• Option d: Pressure (\(P\)) of gas is related to ideal gas law (\(PV = nRT\)), not molar mass calculation.

Answer:

B. By adding the molar mass of Carbon to twice the molar mass of Oxygen