Problem 69 - Chemistry and Chemical Reactivity

Question

Which of the following compounds (NO, CO, MgO, or CaO) has the highest weight percent of oxygen?

Step-by-Step Solution

Answer

CO has the highest weight percent of oxygen at 57.12%.

Step 1: Determine Molecular Weight of Each Compound

To find the weight percent of oxygen, we first need to determine the molecular weight of each compound. - The molar mass of NO is: - N: 14.01 g/mol - O: 16.00 g/mol - Total: 14.01 + 16.00 = 30.01 g/mol - The molar mass of CO is: - C: 12.01 g/mol - O: 16.00 g/mol - Total: 12.01 + 16.00 = 28.01 g/mol - The molar mass of MgO is: - Mg: 24.31 g/mol - O: 16.00 g/mol - Total: 24.31 + 16.00 = 40.31 g/mol - The molar mass of CaO is: - Ca: 40.08 g/mol - O: 16.00 g/mol - Total: 40.08 + 16.00 = 56.08 g/mol.

Step 2: Calculate Weight Percent of Oxygen in Each Compound

Weight percent of oxygen is calculated using the formula \[ \text{Weight percent of } O = \left( \frac{\text{molar mass of } O}{\text{molecular weight of compound}} \right) \times 100 \%\]- For NO: \[ \left( \frac{16.00}{30.01} \right) \times 100 \% = 53.32\% \]- For CO: \[ \left( \frac{16.00}{28.01} \right) \times 100 \% = 57.12\% \]- For MgO: \[ \left( \frac{16.00}{40.31} \right) \times 100 \% = 39.68\% \]- For CaO: \[ \left( \frac{16.00}{56.08} \right) \times 100 \% = 28.53\% \]

Step 3: Compare the Weight Percentages

Now, compare the weight percentages calculated for each compound: - NO: 53.32% - CO: 57.12% - MgO: 39.68% - CaO: 28.53% Clearly, CO has the highest weight percentage of oxygen at 57.12%.

Key Concepts

Molecular Weight Calculation

To determine the oxygen weight percent in a compound, we start by calculating its molecular weight. This step is crucial because it involves summing up the atomic masses of each element in the compound. This sum gives us the total molar mass, which is used to find weight percentages. For instance, to find the molecular weight of nitric oxide (NO), you add the atomic masses of nitrogen (N) and oxygen (O). Nitrogen has an atomic mass of 14.01 g/mol, and oxygen has 16.00 g/mol. When you add these together, \[ \text{N} (14.01 \text{ g/mol}) + \text{O} (16.00 \text{ g/mol}) = 30.01 \text{ g/mol}. \]This calculated total is the molecular weight of NO. This method is universally applied to determine the molecular weight of any compound. Simply sum the atomic masses of all constituent elements.

Molar Mass

Molar mass is the weight of one mole of a compound, usually expressed in grams per mole (g/mol). It's essentially the same as molecular weight but refers specifically to the mass of one mole of a substance. Understanding molar mass is vital because it allows us to convert between the amount of substance and its weight in grams. Each element has its unique atomic molar mass found on the periodic table. Simply add up these values to get the molar mass of a compound. Let's take CO, carbon monoxide, as an example. Carbon has an atomic mass of 12.01 g/mol, and oxygen’s is 16.00 g/mol. The molar mass of CO would therefore be:\[ \text{C} (12.01 \text{ g/mol}) + \text{O} (16.00 \text{ g/mol}) = 28.01 \text{ g/mol}. \]This molar mass helps in calculating other properties like the weight percent of each element in a compound.

Comparing Compounds

When comparing compounds to identify which has the highest percentage of a specific element, like oxygen, we rely on the weight percent. This enables us to determine how much of the compound's weight is due to the target element. Take for example, the comparison between NO, CO, MgO, and CaO. Each has different molecular structures and weights, impacting the oxygen percent. With calculations done before, we find CO has a weight percent of oxygen at 57.12%. The calculation is straightforward; we take the molar mass of oxygen and divide it by the molar mass of the entire compound, then multiply by 100 for a percentage:\[ \frac{\text{O molar mass}}{\text{Compound molar mass}} \times 100\% \]Different compounds offer different results, highlighting diverse properties and uses in chemical processes.

Chemical Composition Analysis

Understanding a compound's chemical composition is essential for various scientific and practical applications. Chemical composition analysis involves determining the percentage by weight of each element in a compound. This helps in predicting chemical behavior, reactivity, and suitability for particular applications. For instance, the analysis tells us CO consists heavily of oxygen, making it relevant in studies concerning oxidation processes. During such analysis, knowing how to perform molecular weight calculations and molar mass assessments are basic yet critical skills. By comprehending the contribution of each element to the total molecular weight, we identify patterns, reactivity, and characteristics of compounds. In industrial contexts, this analysis guides the synthesis of compounds with desired properties, enhancing their potential applications.