20. in which substance does bromine have an oxidation number of +3?\n1) kbro\n2) kbro₃\n3) kbro₂\n4) kbro₄

Explanation:

Step1: Recall oxidation - number rules

The oxidation number of potassium (K) is +1 and of oxygen (O) is -2 in these compounds. Let the oxidation number of bromine be (x). The sum of oxidation numbers in a neutral compound is 0.

Step2: Calculate for (KBrO)

For (KBrO), we have ((+1)+x+(-2)=0). Solving for (x): (x - 1=0), so (x = + 1).

Step3: Calculate for (KBrO_3)

For (KBrO_3), ((+1)+x+3\times(-2)=0). Expanding gives (1 + x-6 = 0), then (x=+5).

Step4: Calculate for (KBrO_2)

For (KBrO_2), ((+1)+x + 2\times(-2)=0). Expanding gives (1+x - 4=0), then (x=+3).

Step5: Calculate for (KBrO_4)

For (KBrO_4), ((+1)+x+4\times(-2)=0). Expanding gives (1+x - 8=0), then (x = + 7).

Answer:

3. (KBrO_2)