The diffraction pattern of crystalline solid gave a peak at $20=60^{\circ}$. What is the distance ( in cm ) between the layers which gave this peak?
( $\lambda$ of $X$-rays is $1.54 \mathring{A}$ ) $\left(\sin 30^{\circ}=0.5, \sin 60^{\circ}=0.866 ; n=1\right)$
(a) $8.89 \times 10^{-8}$The concentration of 1 L of $\mathrm{CaCO}_3$ solution is 1000 ppm . What is its concentration in mol $\mathrm{L}^{-1}$ ?
$$ (\mathrm{Ca}=40 \mathrm{u}, \mathrm{O}=16 \mathrm{u}, \mathrm{C}=12 \mathrm{u}) $$
The $E^{-}$of $M\left|M^{2+} \| \mathrm{Cu}^{2+}\right| \mathrm{Cu}$ is 0.3 V .
At what concentration of $\mathrm{Cu}^{2+}\left(\mathrm{in} \mathrm{mol} \mathrm{L} \mathrm{L}^{-1}\right)$, the $\mathrm{E}_{\mathrm{cel}}$ value becomes zero ? $\left(\frac{2.303 R T}{F}=0.06\right)$
(Conc. of $\mathrm{M}^{2+}=0.1 \mathrm{M}$ )