Solutions and pH Chemistry

Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion. The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium.

$HA,  \alpha =\sqrt{\displaystyle\frac{10^{-5}}{0.1}}=0.01$ 
(A) On adding $HCl, \left [ HA \right ]=\frac{0.1}{2},\left [ HCl \right ]=\displaystyle\frac{10^{-3}}{2}$
$HCl \rightarrow H^{+}+Cl^{-}$
$HA \rightleftharpoons H^{+}  +A^{-}$
$\displaystyle\frac{0.1}{2}\left ( 1- \alpha  \right )\left (\displaystyle\frac{10^{-3}}{2}+\displaystyle\frac{0.1 \alpha }{2}  \right ) \displaystyle\frac{0.1 \alpha }{2} $
$\Rightarrow 10^{-5}=\displaystyle\frac{\displaystyle\frac{0.1\alpha }{2} \times \left (\displaystyle\frac{10^{-3}}{2}+\displaystyle\frac{0.1 \alpha }{2}  \right ) }{\displaystyle\frac{0.1}{2}\left ( 1-\alpha  \right )}$
Neglecting $\alpha $
$10^{-5}=\alpha \times \left ( \displaystyle\frac{10^{-3}}{2}+\displaystyle\frac{0.1\alpha  }{2} \right )$
$\Rightarrow 0.1 \alpha ^{2}+10^{-3} \alpha -2\times 10^{-5}=0$
$\Rightarrow  \alpha ^{2}+10^{-2}\alpha -2\times 10^{-4}=0$
$\Rightarrow \alpha =\displaystyle\frac{-10^{-2}+\sqrt{10^{-4}+8\times 10^{-4}}}{2}=\displaystyle\frac{2\times 10^{-2}}
{2}=2$
Which is similiar to initial.
(B) In case of two weak acids
$\left [\mathrm H^{+}  \right ]=\sqrt{10^{-5}\times \frac{0.1}{2}+2\times 10^{-6}\times \displaystyle\frac{0.5}{2}}$
$=\sqrt{\displaystyle\frac{10^{-6}}{2}+\displaystyle\frac{10^{-6}}{2}}=10^{-3}$
$\alpha =\displaystyle\frac{10^{-5}}{10^{-3}}=10^{-2}$
which is same as earlier
(C) $HNO _{3}\rightarrow H^{+}+NO _{3}^{-}$
$\displaystyle\frac{0.1}{2}       \displaystyle\frac{0.1M}{2}$
$HA \rightleftharpoons H^{+}   +  A^{-}$
$\displaystyle\frac{0.1M}{2}\left ( 1-\alpha  \right )  \displaystyle\frac{0.1}{2}+\displaystyle\frac{0.1}{2}\alpha                
\displaystyle\frac{0.1}{2}\alpha$
$\Rightarrow 10^{-5}=\displaystyle\frac{\frac{0.1\alpha }{2}\times \displaystyle\frac{0.1 }{2} \left (1+\alpha  \right )  }{\displaystyle\frac{0.1}{2}\left (1-\alpha  \right )}$
Neglecting $\alpha $ due to common ion effect.
$\Rightarrow 10^{-5}=\displaystyle\frac{0.1 \alpha }{2}$
$\Rightarrow \alpha =2\times 10^{-4}$
Hence, it decreases from $0.01  to  2\times 10^{-4}$.

Succus entericus, or intestinal juice, is slightly alkaline in nature. A pH of 7.8 is the standard physiological value for this secretion in the small intestine.

Plants grow best in neutral or slightly acidic pH. Slight acidity favours tree growth and forms forests. Slight alkalinity is however, helpful in growth of grasslands and some crop plants like legumes. Hence, for most plants a pH value of 6 to 7 is favourable.

Soil pH is in the range of 6 to 7 for most plants but some prefer acid or alkaline conditions. At this pH soil organic matter and structure is very good. A lot of micro-organisms, that support plant growth can live in the soil at this pH.

Soil pH is important because it influences several soil factors affecting plant growth, such as (1) soil bacteria, (2) nutrient leaching, (3) nutrient availability, (4) toxic elements and (5) soil structure. Bacterial activity that releases nitrogen from organic matter and certain fertilizers is particularly affected by soil pH, because bacteria operate best in the pH range of 5.5 to 7.0. Plant nutrients leach out of soils with a pH below 5.0 much more rapidly than from soils with values between 5.0 and 7.5. Plant nutrients are generally most available to plants in the pH range 5.5 to 6.5. For most plants, the optimum pH range is from 5.5 to 7.0.

$1 \ ppm = 1 \ mg/L = 10^{-3} g/L$

Water sample contains $1 \ ppm$ urea concentration.

$\therefore \ 10^{-3} \ g$ of urea in $ 1 \ L$

$x \ g$ urea in $0.05 \times 10^{-3} \ L$

$x= 0.05 \times 10^{-6} \ g$

$60 \ g$ urea $=6.023 \times 10^{23} \ molecules$

$0.05 \times 10^{-6} \ g = n \ molecules$

$n = \cfrac {6.023 \times 10^{23} \times 0.05 \times 10^{-6}}{60}$

$=0.005 \times 10^{17}$

$=5 \times 10^{14} \ molecules$

Lead is the major heavy metal pollutant released by the vehicular exhausts. It persists in the air and precipitates with the rains. In reaches the human body when consumed through water or inhaled as suspended particle. At the concentration of 30μg/100ml in blood, it is considered poisoning as it can cause aplastic anaemia, tumour and cancer.

Lead is the major heavy metal pollutant released by the vehicular exhausts. It persists in the air and precipitates with the rains. In reaches the human body when consumed through water or inhaled as suspended particle. At the concentration of 30μg/100ml in blood, it is considered poisoning as it can cause aplastic anaemia, tumour and cancer.

Aspirin is a weak acid with pKa = 3.5. In the stomach (pH 2-3), pH < pKa, so it remains mostly unionized (protonated). In the intestine (pH 8), pH > pKa, so it becomes ionized (deprotonated).

Density of Brine$=\rho _{b}=1.2g/cc$