A buffer at pH 7.45 is prepared by mixing solutions of KH2PO4 and K2HPO4. Which of the following ratios of [base]/[acid] is required? For phosphoric acid, Ka1 = 7.5 × 10-3 Ka2 = 6.2 × 10-8 Ka3 = 4.2 × 10-13

The pH of the mixed buffer will be

= 1.737

Explanation:

Buffer is prepared by mixing solutions of KH₂PO₄ and K₂HPO₄

H₂PO₄⁻ ⇄  HPO₄²⁻ + H⁺

Using Henderson equation

⇒         pH = pKa₂ + log

⇒      7.45  = -log(6.2 x 10⁻⁸) + log

⇒     log = 7.45 - 7.2

⇒           =

⇒          = 1.737

So, pH of Buffer solution is equal to 1.737

(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