Final answer:
The density of Metal A most closely matches option D, 6.5 g/cm³, when compared to the observed density reference of 6.67 g/cm³.
Step-by-step explanation:
The student is asking about the density of Metal A, and the options provided are various values in grams per cubic centimeter (g/cm³). Density is calculated by dividing the mass (M) by the volume (V), as given by the formula D = M/V. Based on the reference information provided, we can infer that the X-ray density of a certain material is 6.806 g/cm³, which is comparable to the observed density of 6.67 g/cm³. When comparing this information with the options provided for Metal A's density, the closest match is option D, 6.5 g/cm³, even though it is slightly less than the observed density. In chemistry, understanding density is important for identifying materials and predicting their behavior. Other related key concepts include mass-to-volume ratio and molar volume.