7.00 g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molar mass of 70. g/mol, is burned completely in excess oxygen, and the mass of the products carefully measured. 21.96 g of carbon dioxide and 8.99 g of water are formed as products. a) How much carbon, hydrogen and oxygen is in 7.00 g of Compound X

5.993 g C

1.01 g H

0 g O

Explanation:

Let's consider the combustion of the unknown compound X.

X + O₂ = CO₂ + H₂O

Due to the law of conservation of mass, all the C in CO₂ and all the H in H₂O come from X.

In CO₂, there are 12.01 g of C per 44.01 g of CO₂. The mass of C in 21.96 g of CO₂ is:

21.96 g CO₂ × (12.01 g C/44.01 g CO₂) = 5.993 g C

In H₂O, there are 2.02 g of H per 18.02 g of H₂O. The mass of H in 8.99 g of  H₂O is:

8.99 g H₂O × (2.02 g H/ 18.02 g H₂O) = 1.01 g H

If we sum the mass of H and the mass of C, we get

5.993 g + 1.01 g = 7.00 g

which is the mass of X. Then, X has no oxygen

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