Sieve size 10 mm 5 mm 2.5 mm 1.25 mm 630 µm 315 µm 160 µm Pan

Weight

retained (g)

45

123

169

184

189

133

88

76

Sieve Size Weight

Retained (g)

Cumulative Weight

Retained (g)

Cumulative % Weight

Retained (%)

10.0 mm 45 45 4.5

5.0 mm 123 168 16.7

2.5 mm 169 337 33.5

1.25 mm 184 521 51.7

630 µm 189 710 70.5

315 µm 133 843 83.7

160 µm 88 931 92.5

Total 931

Problem 3 (4 Points)

Total (g)

1007

Note: Do not use the total weight of the

aggregates for the calculation of

the fineness modulus, instead use

the total weight of all the specified

sieves from 10mm to 160µm

Sample Calculations (for 1.25mm sieve)

Cumulative amount retained (g) = 45 + 123 + 169 + 184 = 521

Cumulative Retained (%) = (521/1007) = 51.7%

Fineness Modulus = (4.5 + 16.7 + 33.5 + 51.7 + 70.5 + 83.7 + 92.5) / 100 = 3.53

17.5 A Zn/Zn2+ concentration cell is constructed in which both electrodes are pure zinc. The Zn2+

concentration for one cell half is 1.0 M , for the other, 10-2 M . Is a voltage generated between the two cell halves?

If so, what is its magnitude and which electrode will be oxidized? If no voltage is produced, explain this result.

Solution

This problem calls for us to determine whether or not a voltage is generated in a Zn/Zn2+ concentration

cell, and, if so, its magnitude. Let us label the Zn cell having a 1.0 M Zn2+ solution as cell 1, and the other as cell 2.

Furthermore, assume that oxidation occurs within cell 2, wherein [Zn22 ] = 10-2 M. Hence,

Zn2 + Zn12+ Zn2

2+ + Zn1

and, employing Equation 17.20 leads to

V = 0.0592

2log

Zn22

Zn12

=

0.0592

2log

102 M

1.0 M

= + 0.0592 V

Therefore, a voltage of 0.0592 V is generated when oxidation occurs in the cell having the Zn2+ concentration of

10-2 M.