How many atoms of Ba would be equal to 11.3 g of Ba?

4.96 x 10²²atoms

Explanation:

Given parameters

Mass of Ba  = 11.3g

Unknown:

Number of atoms  = ?

Solution:

To solve this problem, we need to find the number of moles of Ba first and then the number of atoms it contains.

    Number of moles  =  

  Molar mass of Ba = 137.3g/mol

  Number of moles  =   = 0.08mole

 1 mole of a substance contains 6.02 x 10²³ atoms

  0.08 mole of Ba will contain 0.08 x 6.02 x 10²³ atoms  = 4.96 x 10²²atoms

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j