The low melting point of manganese in the 1st transition series is due to:

1. strong metallic bond due to d¹⁰ configuration

2. weak metallic bond due to d⁵ configuration

3. weak metallic bond due to d⁷ configuration

4. none of the above

Which of the following solid salt on heating with K₂Cr₂O₇ and Conc. H₂SO₄ orange,red vapours are evolved which turn aquous NaOH solution yellow?

1. NaBr

2. NaCl

3. NaNO₃

4. NaI

Fe is made passive by :

1. dil . H₂SO₄

2. dil. HCl

3. Conc. HNO₃

4. Conc. H₂SO₄

Which of the following element does not show the variable oxidation state?

1. Fe

2. Mn

3. Cu

4. Zn

Basic oxide amongst the following is:

1. CrO

2. Cr₂O₃

3. CrO₃

4. Cr₂O₄