2,4-Dichlorophenoxyacetic acid ("2,4-D") is a widely used herbicide with the molecular formula C8H6Cl2O3. The pKa of 2,4-D is 2.73. A certain water-based herbicide product contains 230 gL−1 of 2,4-D. What is the pH of the 2,4-D solution?

Explanation:

C₈H₆Cl₂O₃

mol weight

= 8 x 12 + 6 x 1 + 35.5 x 2 + 3 x 16

96 + 6 + 71 + 48 = 221 g

230 g = 230 / 221 mol = 1.04 M solution

pKa = 2.73

Ka = 10⁻²°⁷³

= 1.86 x 10⁻³

Let the compound be represented by KH

KH = K⁻ + H⁺

a        0       0

a - x      x        x  

x ² / (a - x)  = Ka

x² / (1.04 - x) = .00186

x is very small so 1.04 - x = 1.04

x² / 1.04 = .00186

x² = .0019344

x = .044

= 44 x 10⁻³

[ H⁺ ] = 44 x 10⁻³

pH = - log ( 44 x 10⁻³)

= 3 - log 44

= 1.35

some sources quote the lethal dose, for an average 170lbs opiate-naive individual is between 75 and 375 mg

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied