Tag: chemistry

We know that, 1 molecule of water consists of 10 electrons (2 electrons each of two hydrogen atoms and 8 electrons of one oxygen atom).
The number of molecules present in 1.8 g of water.
$18 : g : of : H _2O\xrightarrow[]{contains}6.023\times 10^{23}molecules$
$\Rightarrow1.8 : g : of : H _2O : contains : '! x' : molecules$
$x=\dfrac{1.8\times 6.023\times 10^{23}}{18}$
$=\dfrac{ 6.023\times 10^{23}}{10}=6.023\times 10^{22}molecules$.
$\therefore$ Number of electrons in 1.8 g of water $=6.023\times 10^{22}\times10=6.023\times 10^{23}$

Mass of one electron is $9.108\times 10^{-31} kg$.

Mass of electron $\displaystyle 9.108\times 10^{-31}kg$.
The number of electrons that weigh 1 kg will be $\frac {1}{\displaystyle 9.108\times 10^{-31}}$
The Avagadro number is $\displaystyle 6.023\times 10^{23}$.    
The number of moles of electrons that weigh 1 kg will be
$\frac {1}{\displaystyle 9.108\times 10^{-31} \times \displaystyle 6.023\times 10^{23}}=\displaystyle \frac{1}{9.108\times 6.023}\times 10^{8}$

Plants can neither grow in too acidic conditions nor grow in too basic conditions. Thus for the proper growth of the plant optimum pH of the soil has to be maintained.

$ N _{1}V _{1} (Na _{2}CO _{3}) = N _{2}V _{2} (A)$
$ N _{1}V _{1} (Na _{2}CO _{3}) = N _{2}V _{2}(B)$
$ N _{1} = 1 , V _{1} = 26ml, V _{2} = 10ml, V _{3} = 40ml$
Normality of A
$ N _{2} = \dfrac{N _{1}V _{1}}{V _{2}} = \dfrac{1 \times 26}{10} = 2.6 N $
Normality of B
$ N _{3}= \dfrac{N _{1}V _{1}}{V _{3}} = \dfrac{1 \times 26}{40} = 0.65 N $
if we mix A & B then
$ N _{1}V _{1} + N _{2} V _{2} = N _{3} (V _{1}+V _{2})$
$ 2.6 V _{1}+0.65V _{2} = 1 \times 1000 $
$ 2.6V _{1}+ V _{2} + 0.65 V _{2} = 1000 ...(1)$
$ V _{1}+V _{2} =1000 ...(2)$
multiply $eq^{n}$ (2) by 0.65 
$ 0.65 V _{1}+0.65V _{2} = 650 ...(3)$
$ V _{2} = 820.6 ml$
$ V _{1} = 1000 - 820.6 = 179.4 ml $
option "a" correct.

$ KMnO _{4}+KNO _{2}$
$ 0.18 N $ 25 ml
V = ? 0.21 N
we know $ N _{1}V _{1}= N _{2}V _{2}$
$ 0.18 \times V _{1} = 0.21 \times 25 $
$ V _{1} = \dfrac{0.21 \times 25}{0.18 }$
$ \boxed{V _{1} = 29.17 ml}$
Answer option C

Indigestion can lead to a feeling of fullness, burping, heartburn (due to gastric acid reflux), etc. Thus an antacid can neutralize the effect of an excess of acid and hence it can be consumed for some relief from heartburn, indigestion, acidity, etc.

Calcium hydroxide called slaked lime is an inorganic compound. It is a colorless crystal and is obtained when calcium oxide is mixed with water. It is used in preparation of dry mixes for painting and white washing.

Caustic soda is sodium hydroxide which is a strong base and so it has high basicity value on $pH$ scale. It is widely used in acid-base titrations to neutralize various strong or weak acids like sulfuric acid.