When 0.422g of phosphorus is burned, 0.967g of a white oxide is obtained.
a. determine the empirical formula of the oxide
b. write a balanced equation for the reaction of phosphorus and molecular oxygen on the basis of this empirical formula

Answer :

(a) The empirical formula of a compound is,

(b) The balanced chemical equation will be:

Solution :  Given,

Mass of phosphorus = 0.422 g

Mass of white oxide = 0.967 g

Molar mass of phosphorus = 31 g/mole

Molar mass of oxygen = 16 g/mole

First we have to calculate the mass of oxygen.

Mass of oxygen = Mass of white oxide - Mass of phosphorus

Mass of oxygen = 0.967 - 0.422

Mass of oxygen = 0.545 g

Now convert given masses into moles.

Moles of P =

Moles of O =

For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For P =

For O =

The ratio of P : O = 1 : 2.5

To make this ratio in a whole number we multiple ratio by 2, we get:

The ratio of P : O = 2 : 5

The mole ratio of the element is represented by subscripts in empirical formula.

The Empirical formula =

The balanced chemical equation will be:

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

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explanation: