Question

At STP a 7.49-gram sample of an element has a volume of 1.65 cubic centimeters. What is the element?

Answer 1

The element is titanium, `"Ti"`.

Explanation:

The density (`ρ`) of anything is its mass (`m`) divided by its volume (`V`).

`color(blue)(bar(ul(|color(white)(a/a)ρ = m/Vcolor(white)(a/a)|)))" "`

In this problem,

`m = "7.49 g"`
`V = "1.65 cm"^3`

∴ `ρ = m/V = "7.49 g"/("1.65 cm"^3) = "4.54 g/cm"^3`

We consult a list of chemical elements sorted by density.

`ρ"/g·cm"^"-3"color(white)(m)"Element"color(white)(m)"Symbol"color(white)(m)"At. No."`
`stackrel(—————————————————)(color(white)(m)4.47color(white)(mm)"Yttrium"color(white)(mmll)"Y"color(white)(mmmm)39)`
`color(white)(m)4.54color(white)(mm)"Titanium"color(white)(mm)"Ti"color(white)(mmmll)22`
`color(white)(m)4.79color(white)(mm)"Selenium"color(white)(mml)"Se"color(white)(mmmll)34`

The three most likely elements are `"Y, Ti"`, and `"Se"`.

The element is probably titanium, `"Ti"`.