Final answer:
There are two distinct compounds in the formulas given: MgCl2 and Na3AsO2. The coefficients indicate the quantity but not the count of compounds, leading to the answer B) 2. The answer involves understanding ionic compounds and the concept of moles in chemistry.
Step-by-step explanation:
In the context of the question provided, there are two compounds in the formulas given: MgCl2 and Na3AsO2 (assuming 'AsO2' refers to arsenite, in which case it would be properly written as Na3AsO3). The coefficients (6 and 5) in front of the formulas indicate the number of moles or molecules of each compound in question but do not affect the count of distinct compounds. Therefore, the correct answer to the question is B) 2.
When writing formulas for ionic compounds, it's essential to use the correct charge balance between cations and anions. For instance:
- sodium bromide: NaBr
- lithium chloride: LiCl
- magnesium oxide: MgO
The number of moles present in a given amount of substance can be calculated using the molar mass of the compound. Molar mass serves as the conversion factor between grams and moles. To calculate the number of moles from grams, you divide the mass of the substance by its molar mass. Similarly, to find out how many atoms of a given element are in a number of molecules, you'd use Avogadro's number (6.022×1023 molecules per mole) and the stoichiometry of the compound.