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.

Pick the odd one out with respect to the type of reaction that would take place between the following substances:

Match the following:

A. BaCl2 + Na2SO4 BaSO4 + 2NaCl	(i) Combination reaction
B. Mg + H2O MgO + H2	(ii) Double displacement reaction
C. 2KClO3 2KCl + 3O2	(iii) Decomposition reaction
D. C + O2 CO2	(iv) Displacement reaction

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

Which of the following is not a chemical change?

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?

When iron nails are placed in the blue coloured solution of copper sulphate, the solution turns green. Which type of chemical reaction does it represent?

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 true about the reaction of copper turnings with the silver nitrate solution?

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?