Butene, used as the monomer for polybutene, is composed of 85.7% and 14.3% by mass. if the density of butene is 2.50 g/l at stp, what is the molecular formula of butene?

C₄H₈

Explanation:

In the first, you should know the ideal gas law. One of the formula for this concept is:

MW = (δ*R*T) / P where:

MW is molecular weight, δ is density 2,50 g/L, R is the gas constant (0,082 (atm*L) / (mol*K) ), T is temperature (273,15 K at STP) and P is pressure (1 atm).

So:

MW = [2,50 g/L * 0,082 (atm*L) / (mol*K) * 273,15 K ] / 1 atm

MW = 56 g/mol

Then the problem says than butene is composed by 85,7% (of carbon) and 14,3 % (of hydrogen). So:

Carbon mass: 56 g/mol * 85,7% = 48 g/mol / 12 g/mol ( atomic mass of carbon = 4 carbon atoms.

And, hydrogen mass: 56 g/mol * 14,3% = 8 g/mol / 1 g/mol ( atomic mass of hydrogen = 8 hydrogen atoms.

Thus, the molecular mass of butene is: C₄H₈

I hope it helps!

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.