Physical And Ch...

If we keep moistened iron nails for a few days, the iron nails get covered with a reddish-brown substance, which is different from iron. Which of the following is/are not the change(s) that take(s) place?

a. The state as well as the composition of iron changed.
b. The changes that took place were reversible.
c. A new substance was formed.

Iron objects, such as the wheels of a bicycle, are coated with which of the following metals to give them a shining appearance?

Identify the incorrect statement(s).

Statement I: All physical changes are spontaneous, but chemical changes have to be induced.
Statement II: All changes, physical as well as chemical, involve energy exchanges.

Which of the following are redox reactions?

I. Cu + 2H₂SO₄ → CuSO₄ + 2H₂O + SO₂
II. BaCI₂ + H₂SO₄ → BaSO₄ + 2HCI
III. Zn + H₂SO₄ → ZnSO₄ + H₂
IV. 2KNO₃ + H₂SO₄ → 2HNO₃ + K₂SO₄

When copper turnings are added to a clear solution of silver nitrate, a greyish deposit of silver is observed after some time. Silver gets precipitated and copper (II) nitrate is also formed. The reaction is an example of __________ reaction and ________ is more reactive than ________.

Zinc oxide (ZnO) reacts with carbon (C) to produce zinc (Zn) and carbon monoxide (CO). The balanced chemical equation for the given reaction is ZnO (s) + C (s) → Zn (s) + CO (g). Which of the following substances is reduced in the given reaction?

Consider the following reaction:

MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O

Which of the following is getting oxidised in this reaction?

Which of the following statements is not true about a substance that goes rancid?

Suppose, a reaction takes place between magnesium and oxygen to form magnesium oxide. Where will magnesium oxide be represented in the chemical equation?

Which of the following phenomena is not an indication of a chemical change?