JEE Main 2023 · 11 April · evening · Single correct · +4 / −1
For a chemical reaction A+B → Product, the order is 1 with respect to A and B.
What is the value of x and y ?
| Rate mol L⁻¹ S⁻¹ | [A] mol L⁻¹ | [B] mol L⁻¹ |
|---|---|---|
| 0.10 | 20 | 0.5 |
| 0.40 | x | 0.5 |
| 0.80 | 40 | y |
- (a) 80 and 4
- (b) 160 and 4
- (c) 80 and 2
- (d) 40 and 4
Answer and solution
Answer (c) 80 and 2
Solution
Chemistry ma’am · 4 steps
Find k from the complete first row, then use the same k to unlock each missing value.
- Write the rate law. First order in A and first order in B means the rate is k[A][B]. The first row has every value, so it gives k.
k = 0.10/(20 × 0.5) = 0.01 L mol⁻¹ s⁻¹
- Find x. Row 2: 0.40 = 0.01 × x × 0.5, so x = 0.40/0.005 = 80. As a check, [B] is unchanged and the rate is 4 times larger, so [A] must also be 4 times larger: 4 × 20 = 80.
- Find y. Row 3: 0.80 = 0.01 × 40 × y, so y = 0.80/0.4 = 2. As a check, the rate is 8 times row 1 and [A] is 2 times larger, so [B] must be 4 times larger: 4 × 0.5 = 2.
- So. x = 80 and y = 2, which is option (c).
The idea to keep. When a rate table has blanks, use the one complete row to find k. Then each other row is a single equation with one unknown.
Answer from the NTA final answer key. Solution by PrepWiser.