**BMAT Prep Question Analysis - Q171 & Q245**

**Q171 Zn and Cu****²**** undergo an equimolar redox reaction, whereby ****Zn**^{2+}** is formed. After the reaction, what is the oxidation number of Cu?**

a. 1

b. 0

c. -1

d. 2

e. -2

**Q245 In the figure below, the square ABCD and the triangular region ACE each have area 36.**

Which is the perimeter of the triangle ACD?

**Answer and Explanation**

**Q171** **Answer**: b. 0

**Explanation**: This equimolar redox (reduction-oxidation) reaction, 2 electrons are traded between these two metals. Since zinc loses 2 electrons, that must mean that Cu?* gains 2 electrons in the reaction and forms an uncharged Cu atom. The oxidation number of a monoatomic species is equal to its net charge (zero in this case)

**Q245 Answer: **b. 12 + 6√2

**Explanation**: Since the area of square ABCD is 36, we deduce that each side of the square measures √36 = 6. We fherefore now know that AD = CD = 6.

The distance AC is calculated using the Pythagorean theorem and is equal to √(36 + 36) i.e. √72 or 6√2.

Thus the perimeter of the triangle ACD is 6+6+6√2 = 12+ 62. Note that the information given about ACE is not needed to solve this question.

Drafted by Quincy (BMAT Prep)