Question

the density of 10% by mass of kcl solution in water is 1.06gml-1 calculate molarity
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Answer 1

Given:-

• Density of KCl solⁿ is 1.06g / ml .
• Concentraⁿ of solⁿ is 10% ( w/w ) .

To Find:-

• The molarity of the solution.

Formula Used:-

$\sf We \:can \:calculate\: molarity \:using ,$

$</p><p>\large\orange{\underline{\boxed{\green{\mathscr{\dag M\sf{olarity}\:\:=\:\:\dfrac{\mathscr{N}o\:of\:moles\:of\:solute}{\mathscr{V}olume\:of\: \mathscr{S}olution (in\:L) }}}}}}$

Solution:-

$\purple{\rm{\hookrightarrow Firstly\: let's\: calculate \: molar\:mass:-}}$

$\sf\bullet Molar \:mass \:of\: KCl \:=\: 39 g + 35.5g = 74.5$

$\sf\bullet Density\:of\: solution\:(\rho)\:=\:1.06g/ml$

Here it's given its concentration is 10% ( w/w) . So in 100g of solution there will be 10g of solute.

$\underline{\pink{ \tt \leadsto For\:100g\: solution:-}}$

$\tt Now \: let's \: find \: Volume\: using\: above\:data$

$\tt:\implies Density (\rho)=\dfrac{Mass}{Volume}$

$\tt:\implies 1.06g/ml=\dfrac{100g}{V}$

$\tt:\implies V =\dfrac{100}{1.06}$

$\underline{\boxed{\red{\tt{\longmapsto \:\: Volume\:\:=\:\:94.333ml}}}}$

_________________________________________

$\underline{\pink{ \tt \leadsto Now\:calculate\: number\:of\:moles:-}}$

$\tt:\implies n(Moles)=\dfrac{Given\:weight}{GAM(Gram\: Atomic\:mass}$

$\tt:\implies n =\dfrac{10g}{74.5g}$

$\underline{\boxed{\red{\tt{\longmapsto \:\: n(Moles)\:\:=\:\:0.134}}}}$

_________________________________________

$\underline{\pink{ \tt \leadsto Now\:calculate\: Molarity:-}}$

$\tt:\implies Molarity(M)=\dfrac{Number\:of\:moles}{Volume (in\:L)}$

$\tt:\implies M =\dfrac{0.314}{\dfrac{94.33}{1000}L}$

$\tt:\implies M=\dfrac{0.314\times1000}{94.33}$

$\underline{\boxed{\red{\tt{\longmapsto \:\: Molarity\:\:=\:\:1.42M}}}}$

$\blue{\boxed{\orange{\bf \dagger Hence\:the\: Molarity\:is\:1.42M.}}}$