Page 215 - Chemistry

Usefull heat = 75X150 = 112.5 kj
100
Let volume of water = V
o
Room temperature = 25 C
o
Boiling point = 100 C
o
Change in temperature, T = 100-25 = 75 C ½ mk
T X mass X C Q 315V = 112500
 75 X V X 4.2 =112.5 V = 112500 ½ mk
1000 1 315
3
V = 357.km ½ mk

32. RFM Na 2CO 3 = 43 + 12 + 48 = 106
Mol. Na 2 CO 3 = 19.6 = 0.8149057
106
Molarity of Na 2 Co 3 = 0.1849057 = 0.73962m
0.25
Na 2 Co 3(aq) + Mg Cl 2(aq) + MgCo 3(s)
Mole ratio Na CO 3 : Mg Cl 2 is 1:1
 mol. Mg Cl 2 Reacted = 0.1849
If 2.0 mol. = 1000cm3 solution mg cl 2
= 0.1849mol = 0.1849 X 1000
2
3
= 92.45 or 92.5 cm

33. i) ACID BASE
1 2
3
½ 0.004 20cm X 0.2 moles
3
= 0.002 moles  ½ 1000cm = 0.004 moles

3
25cm ________ 0.002 moles  ½
3
1000cm ______ ?
3
1000cm X 0.002 moles = 0.08 M ½

ii) 0.08 moles ________________ 10.08 g H 2C 2O 4xH 2O  ½
1 mole __________________ ?

1 mole X 10.08 = 126  ½
0.08 moles
126 _______ H 2C 2O 4xH 2O

18x = 126 – 90  ½
18x = 36
X = 2  ½

34. Mg (g) + 2HCL (aq) ___________ MgCl 2 (aq) + H 2 (g)
3
24g _________________________________ 22.4dm
16g _____________________________________?

3
3
1.6 gx 22.4dm  ½ = 1.4933 dm

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