Answer:
22.5 g
Step-by-step explanation:
If there is a 30% concentration of cobalt chloride in 90g of a water and cobalt chloride solution then:
Mass of Cobalt Chloride
30% of 90 g
= 0.3 × 90
= 27 g
Mass of Water
70% of 90 g
= 0.7 × 90
= 63 g
If a certain amount of water evaporates (note, the mass of cobalt chloride doesn't change), the ratio of cobalt chloride to water changes to 40% : 60%.
Let x be the new mass the water.
Therefore:
[tex]\implies \sf 27 \: g : x \: g = 40\% : 60\%[/tex]
[tex]\implies \sf27 : x = 0.4 : 0.6[/tex]
[tex]\implies \sf \dfrac{27}{x}=\dfrac{0.4}{0.6}[/tex]
[tex]\implies \sf \dfrac{27}{x}=\dfrac{4}{6}[/tex]
[tex]\implies \sf \dfrac{27}{x}=\dfrac{2}{3}[/tex]
[tex]\implies \sf 27 \cdot 3= 2x[/tex]
[tex]\implies \sf 81= 2x[/tex]
[tex]\implies \sf x = 81 \div 2[/tex]
[tex]\implies \sf x=40.5[/tex]
Therefore, the new mass of water is 40.5 g.
To find the mass of water than has evaporated, simply subtract the new mass from the original mass:
[tex]\implies \sf 63 - 40.5 = 22.5\: g[/tex]
Therefore, the mass, in grams, of water that has to evaporate to have a 40% concentration of cobalt chloride is 22.5 g.
Where do water come here?
Cobalt chloride or CoCl_2 doesn't stay in dry state it contains crystals of water in hydrated form
Now coming to question
Amount of Cobalt chloride
Amount ofw water
For 40% concentration of CoCl_2 concentration left =100-40=60%
Let new mass of water be m
Water has to be evaporated
