Asample of calcium oxide (cao) has a mass of 2.80 g. the molar mass of cao is 56.08 g/mol. how many moles of cao does this sample contain?

Answer is "0.05 mol".

Explanation;

We can do calculation by using a simple formula as

n = m/M

Where, n is the number of moles of the substance (mol), m is the mass of the substance (g) and M is the molar mass of the substance (g/mol).

Here,

n = ?

m = 2.80 g

M = 56.08 g/mol

By substitution,

n = 2.80 g /56.08 g/mol

n = 0.0499 mol ≈ 0.05 mol

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