When steam is passed over red hot iron , the substances formed are:
1. Fe2O3 +H2
2. Fe3O4 +H2
3. FeO +H2
4. FeO+ H2 +O2
Which of the following solid salt on heating with K2Cr2O7 and Conc. H2SO4 orange,red vapours are evolved which turn aquous NaOH solution yellow?
Fe is made passive by :
1. dil . H2SO4
2. dil. HCl
3. Conc. HNO3
4. Conc. H2SO4
The iron salt used in blue prints is:
CrO42- (yellow) changes to Cr2O72- (orange) in pH =x and vice versa in pH=y.
The value of x and y is :
Then final products N and O are respectively.
Elements which generally exhibit multiple oxidation states and whose ions in aqueous medium are usually coloured :
2. transition elements
Lanthanoid contraction is caused due to :
1. the appreciable shielding on outer electrons by 4f electrons from the nuclear charge
2. the appreciable shielding on outer electrons by 5d electrons from the nuclear charge
3. the same effective nuclear charge from Ce to Lu
4. the imperfect shielding on outer electrons by 4f electrons from the nuclear charge
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 has the highest melting point?