There are four unknown compounds that are labeled w, x, y, and z. only substance y is soluble in water. compound y could be
1)iron oxide.
2)zinc hydroxide.
3)potassium bromide.
4)silver oxide.

Potassium bromide

Explanation:

Potassium bromide is an ionic compound and it is freely soluble in water as water is polar solvent (with high dielectric constant) so can easily dissolve polar or ionic compounds in it.

"Like dissolved like"

for other compounds they are not soluble in water,

Zinc hydroxide is slightly soluble in water, but very less soluble as compared to potassium bromide.

air

in a tire you fill a tire with air

then a couple days later you check the air pressure in the tire

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