برقی کیمیا، توانائی اور شرحِ تعامل

Written by Dr. Ayesha Nadeem (Chemistry)

ایم ڈی کیٹ · کیمیا · 8 سوالات

نام: ____________________ تاریخ: ____________

What is the oxidation state of manganese in KMnO4?
- A +7
- B +2
- C +6
- D +4
What is the oxidation state of sulphur in H2SO4?
- A +2
- B +6
- C -2
- D +4
In an electrolytic cell, oxidation takes place at the:
- A Cathode
- B Electrolyte only
- C Salt bridge
- D Anode
The standard electrode potential of the standard hydrogen electrode is:
- A 0.00 V
- B +1.00 V
- C +0.34 V
- D -1.00 V
An exothermic reaction has an enthalpy change (delta H) that is:
- A Negative
- B Equal to the activation energy
- C Positive
- D Zero
Zinc has a standard electrode potential of -0.76 V and copper +0.34 V. What is the standard EMF of the Zn-Cu cell?
- A 1.10 V
- B -1.10 V
- C 0.76 V
- D 0.42 V
Raising the temperature increases the rate of a reaction mainly because:
- A The activation energy falls
- B More molecules have energy equal to or above the activation energy
- C The concentration of the reactants rises
- D The products become more stable
A catalyst increases the rate of a reaction by:
- A Increasing the equilibrium yield
- B Being consumed in the reaction
- C Providing a path with lower activation energy
- D Raising the temperature

جوابی کلید

1. A, 2. B, 3. D, 4. A, 5. A, 6. A, 7. B, 8. C

K is +1 and four O atoms are -8 in total. So Mn = +8 - 1 = +7.
Two H atoms give +2 and four O atoms give -8, so S must be +6 to make the molecule neutral.
Oxidation always happens at the anode and reduction at the cathode.
The standard hydrogen electrode is the reference, and its potential is defined as exactly 0.00 V.
Heat is released to the surroundings, so the system loses enthalpy and delta H is negative.
EMF = E(cathode) - E(anode) = 0.34 - (-0.76) = 1.10 V.
A larger fraction of molecules has enough energy to react when they collide. The activation energy itself does not change.
A catalyst offers an alternative route with lower activation energy. It is not consumed and does not change the position of equilibrium.