chem p5 construction lines

[khalida]

what are construction lines? they ask us to draw appropriate lines on graph to calculate value of x. like in jo8 q2
im confused. do we take gradient or wht? or we just take one point on the line. say 5th point?

 

[mawak]

EXAMPLE TO FIND VALUE OF X

Problem You want to know the value of x in blue, hydrated copper(II) sulfate, CuSO4 · x H2O; that is, the
number of water molecules for each unit of CuSO4. In the laboratory, you weigh out 1.023 g of the solid.
After heating the solid thoroughly in a porcelain crucible (see Figure), 0.654 g of nearly white, anhydrous
copper(II) sulfate, CuSO4, remains.
1.023 g CuSO4 · x H2O  heat → 0.654 g CuSO4  ? g H2O
Strategy To find x, we need to know the amount of H2O per mole CuSO4. Therefore, first find the mass of
water lost by the sample from the difference between the mass of hydrated compound and the anhydrous
form. Finally, find the ratio of amount of water lost (moles) to the amount of anhydrous CuSO4.
Solution Find the mass of water.
Mass of hydrated compound =1.023 g
Mass of anhydrous compound, CuSO4 = 0.654
-
Mass of water = 0.369 g
Next, convert the masses of CuSO4 and H2O to moles.
0.369 g H O x
1 mol HO
18.02 g H2O = 0.0205

mol H 2O
0.654 g CuSO4 x
1 mol CuSO4
159.6 g
CuSO4
0.00410 mol CuSO4
The value of x is determined from the mole ratio.
0.0205 mol H O
0.00410 mol CuSO4=2 5.00 mol
H 2O
1.00 mol CuSO4
The water-to-CuSO4 ratio is 5-to-1, so the formula of the hydrated compound is CuSO4 · 5 H2O. Its name is
copper(II) sulfate pentahydrate.

 

[mawak]

CONSTRUCTION LINE

FOR IT U HAVE TO SIMPLY DRAW A TRIANGLE (RIGHT ANGLED INCLUDING HYPOTENUSE AND BASE ETC..U MAY GET THE IDEA)....COVERING MORE THAN HALF OF THE GRAPH

 

[fabfreak]

do we hav to find d gradient afta drawing d construction lines?

 

[mawak]

yes most of the times

 

[khalida]

can u relate it to jo8 q2? thnx

 

[fabfreak]

10x mawak | best of luck :]

 

[K.I.]

hey thanx mawak. good one there bro, helped me a lot..