H2O is a compound. So it's second one.
The answer is D because they would have to make quarries just below the surface to mine
Mineral ores much quicker (Quarries- a large hole/pit under ground used to get stone and minerals)
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You have OH- conc = </span>2.3 ✕ 10−6 m
From the formula, you can observe the ratio of Cu2+ to OH- is 4 : 6 = 2:3
So, for 2.3 ✕ 10−6 m OH-
[Cu2+] =

Answer:
3) an applied electric current
Explanation:
An electric source is used in an electrolytic cell.