When copper(II) oxide is heated with hydrogen gas, water and copper metal is produced. What mass of copper can be obtained if 32.0g of copper(II) oxide is used?
A: 24.3g
B: 25.5g
C: 27.6g

25.5 g

Explanation:

First, you will need a balanced chemical equation

CuO  +  H₂  ==>  H₂O  +  Cu

From the equation above, we can see that for every 1 mole of CuO (copper(II) oxide), 1 mole of Cu (copper) is produced.  

Convert grams of CuO to moles.  You should get 0.402 mol.  Now with the relationship established above, you can see that you should ideally get 0.402 mol.  Convert this to grams.  Your answer should be 25.5 g.

(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