19. What is the %w/v of a solution created using 20g? 20. What is the freezing p

Question

19. What is the %w/v of a solution created using 20g?

20. What is the freezing point depression if 2.5 moles of solute are added to a system? (1mol solute=-1.86C)

21.Write formula of:                                             Name the following:
sodium fluoride              Iron (ii) sulfide                                   N3O4   S2O   Al(OH)3

calcium nitrate                pentaphosphorous trinitrogen             Ca(NO3)2    K3N

cobalt (ii) chloride sulfur trioxide

22.What is the pH of a 2M solution of HCl?

23.A solution has a pH of 4, what is the pOH?

24.A solution has a pOH of 8, what is the [H+]?

25. A solution has a pH of 2. What is the pOH, [OH-], and is this solution acidic or basic?

26.What is the %yield of a reaction if we expected to produce 2g of product but only produced 0.4g?

Explanation / Answer

21) sodium fluoride ------ NaF

calcium nitrate---Ca(NO3)2

Iron (ii) sulfide   or ferrous sulfide --- FeS

pentaphosphorus trinitrogen----P5N3

cobalt (ii) chloride ---- CoCl2

sulfur trioxide ---SO3

N3O4 --- Trinitrogen tetraoxide

S2O ----Disulfur monoxide or sulfur suboxide

Al(OH)3 --- Aluminium hydroxide

Ca(NO3)2 --- Calcium nitrate

K3N --- Potassium nitride

22) 2 M HCl solution means H+ ion concentration is 2.

pH = - log [H+] = -log [2] = - 0.3010

23) Given pH = 4

we know , pH + pOH =14

=>pOH =14 -pH =14 -4 =10

24) Given pOH =8

therefore pH + pOH =14

=> pH +8 =14

=>pH =14-8 =6

Now, [H3O+] = 10-pH =10-6 =0.000001 =1 x 106 M

25) given pH =2

we have pH + pOH =14

=>pOH =14 -2 =12

therefore [OH-] =10-pOH=10-12 =1 x 10-12 M

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