An herbicide is found to contain only c, h, n, and cl. the complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 ml of co2 and 73.30 ml of h2o vapor at stp.

a separate analysis shows that the sample also contains 16.44 mg of cl.

The empirical formula of the compound is C8H14ClN5

C =  44.5%

H =  6.6 %

Cl =  16.4%

N = 32.5%

Explanation:

An herbicide is found to contain only C, H, N, and Cl. The complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 mL of CO2 and 73.30 mL of H2O vapor at STP.

A separate analysis shows that the sample also contains 16.44 mg of Cl. Calculate its empirical formula.  Determine the percentage of the composition of the substance.

Step 1: Data given

Mass of the sample = 100.0 mg

Volume of CO2 = 83.16 mL

Volule of H2O = 73.30 mL

A separate analysis shows that the sample also contains 16.44 mg of Cl.

Step 2: The balanced equation

CwHxNyClz + O2 ⇒ CO2 + H2O

Step 3: Calculate moles of CO2

Moles CO2 = (p*V)/(R*T)

Moles CO2 = (1*0.08316)/(0.08206*273)

Moles CO2 = 0.003712 moles

Step 4: Calculate moles of H2O

Moles H2O  = (1*0.07330)/(0.08206*273)

Moles H2O = 0.003272

Step 5: Calculate moles of Cl

Moles Cl = mass Cl / molar mass CL

Moles Cl = 0.01644 grams / 35.45 g/mol

Moles Cl = 4.64 *10^-4 moles

Step 6: Calculate moles C

CO2 contains 1 mol C

For 0.003712 mol of CO2 we have 0.003712 mol of C

Step 7: Calculate moles of H

H2O contains 2 mole of H

For 0.00372 moles of H2O we have 2*0.003272 = 0.006544 mol H

Step 8: Calculate mass of C and H

0.003712 mol C *12.01g/mol = 0.04458g C

0.006545 mol H *1.01g/mol = 0.006610g H

Step 9: Calculate mass of N

0.1 g - (0.04458g C+ 0.006610g H+0.01644g Cl)=  0.03237g N

moles N = 0.03237 / 14.00 g/mol = 0.002312

Step 10: Calculate mol ratio

C: 0.003712 / 0.000464 = 8

H: 0.006545/ 0.000464 = 14

Cl: 0.000464 / 0.000464 = 1

N: 0.002312 / 0.000464 = 5

The empirical formula of the compound is C8H14ClN5

The molar mass is 215.59 g/mol

Step 11: Determine the percentage of the composition of the substance.

C = ((8*12)/215.59) *100%  = 44.5%

H = ((14*1.01)/215.59)*100% = 6.6 %

Cl = (35.45 / 215.59)*100% = 16.4%

N = ((5*14)/215.59) * 100% = 32.5%

n has four pairs of electrons in the valence shell, electrons repel one another ,n has 7 protons in its nucleus, and since n has 7 protons, it must fill the second shell, giving it 4 pairs of electrons. the electrons form 3 bonds and 1 lone pair of electrons. each pair of electrons repels the other pairs, so they are equally far apart.

so all of the above

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.