UNIT TEST – I (2021-22)
CLASS-XII
CHEMISTRY M:M 20
Q.1 The correct order of the packing efficiency in different types of unit cell is: (1)
a) fcc > bcc < simple cubic
b) fcc > bcc =simple cubic
c) fcc > bcc > simple cubic
d) bcc> fcc < simple cubic
Q.2 The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called ___________. (1)
(a) Cell potential
(b) Cell emf
(c) Potential difference
(d) Cell voltage
Q.3 An electrochemical cell can behave like an electrolytic cell when ______. (1)
(a) E cell= 0
(b) E cell > Eext
(c) Eext > E cell
(d) E cell = Eext
Q. 4 Calculate Molar conductance at infinite dilution for acetic acid .(2)
(given λ m at infinite dilution for HCl=425 ohm-1 cm2 mol-1, λm at infinite dilution for NaCl=188 ohm-1cm2mol-1, λm at infinite dilution for CH3COONa=96 ohm-1cm2mol-1).
Q.5 Which point defect in crystals of a solid does not change the density of the solid and why?(2)
Q.6 ZnO crystal on heating acquires the formula Zn1+xO. Give reason. (2)
Q.7 Give construction and working of fuel cell. (3)
Q.8 An element with molar mass 2.7 X 10-2 kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 X 103 kg m-3, find the nature of the cubic unit cell ? (3)
Q.9 The reduction potentials of Cu2+/Cu and Ag+/Ag electrodes are 0.34V and 0.80V respectively. For what concentration of Ag+ions will the EMF of the cell at 250C is zero? Given that the concentration of Cu2+ is 0.01M. (5)