Given: BO3 + 3Mg → 3MgO + B
1. How many moles of Mg are required if 2 moles of B are produced?

6moles of Mg

Explanation:

The reaction expression is given as:

          BO₃   +    3Mg   →    3MgO    +    B

Given:

Number of moles of B produced  = 2 moles

Unknown:

Number of moles of Mg required  = ?

Solution:

  From the balanced reaction expression:

          1 mole of B is produced from 3 moles of Mg

          2 moles of B will be produced from 2 x 3  = 6moles of Mg

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