Calculate [h3o+] given [oh−] in each aqueous solution.
1. [oh−] = 2.1×10^−11 m
express your answer using two significant figures.
2. [oh−] = 6.5×10^−9 m
express your answer using two significant figures.
3. [oh−] = 4.1×10−4 m
express your answer using two significant figures.
4. [oh−] = 5.5×10−2 m
express your answer using two significant figures.

Balance and in which category does it fit in? single or double displacement or synthesis or decomposition? (a) k2 o → k + o2 (b) na + i2 → nai (c) cu(no3 )2 + naoh → cu(oh)2 + nano3 (d) kclo3 → kcl + o2 (e) ca(no3 )2 + hbr → cabr2 + hno3 (f) sn(oh)2 → sno + h2 o (g) p4 + n2 o → p4 o6 + n2 (h) fe + al2 (so4 )3 → feso4 + al (i) alcl3 + na2 co3 → al2 (co3 )3 + nacl (j) c3 h6 + o2 → co2 + h2 o