Consider the reaction.

mc028-1.jpg

which statement is true at stp? (the atomic mass of zn is 65.39 u.)
2 mol of hcl produce 1 l of h2 gas.
1 l of zn produces 1l of h2 gas.
65.39 g of zn produce 22.4 l of h2 gas.
1 l of hcl produces 1 mol of h2 gas.

65.39g of Zn will produce 22.4L of gas.

Explanation: For a reaction,

2 moles of HCl produces 1 mol of gas.

Molar Volume of gas for 1 mole at STP = 22.4 litres

As seen from the balanced chemical equation, 1 mole of Zn gives 1 mole of gas. Hence 22.4L of gas is produced.

(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