Corundum is the hardest mineral in nature after diamond. For this reason it can only be scratched and worked by it. Mohs' hardness scale proves that corundum is indeed a very hard mineral and almost impossible to scratch. This scale states that the corundum has a hardness of 9.0, which indicates that it cannot be scratched by a drill.
Using the same scale, we can find out the hardness of the mineral exposed in the question. The mineral can be scratched by a drill, which means it has a hardness lower than 8.5, and the mineral cannot be scratched by a nail, which indicates that it has a hardness greater than 6.5. Based on this data, we can guarantee that this meniral is softer than the corundum.
The mineral has a hardness greater than 6.5 (steel nail) and less than 8.5 (drill bit). All other choices have a hardness less than 8.5 but corundum has a hardness of 9.0. *Mohs hardness scale
A general formula of an acid always start with H or the hydronium ion. It has to end with an anion. As acids, these compounds are named starting with the prefix "hydro-," then adding the first syllable of the anion, then the suffix "-ic." Hope this answers the question. <span />
</span>Zn⁰ --- in free elements oxidation number is 0. Zn²⁺SO4²⁻ ---- ionic compound , it has ion Zn²⁺, so oxidation number here is +2. <span>The oxidation number of Zn changes from 0 to +2.</span>
