A pure organic compound weighing 947.4mg was heated in a stream of oxygen. The effluent gas was swept successively through a tube of magnesium perchlorate dessicant weighing 18.6137g and a tube of Ascarite weighing 16.8425g. After several minutes the tubes were sealed and reweighed. The tube containing the magnesium perchlorate weighed 18.6448g and the tube containing the Ascarite weighed 16.9098g.
Calculate the % H and % C in the sample.
If the compound consisted only of C and H, calculate its empirical formula.
Difference between initial and final weight perchlorate = mass H2O
Difference between initial and final weight ascarite = mass CO2
%H = [(mass H2O x 2*atomic mass H/molar mass H2O)/mass original sample]*100 = ?
% C = [(mass CO2 x atomic mass C/molar mass CO2)/mass original sample]*100 = ?
To find the empirical formula, take 100 g sample which gives the percent C and H in grams.
Convert to mols
Find the ratio of C to H with the smallest number being no less than
1.00. Post your work if you get stuck.
Difference between initial and final perchlorate(18.6137-18.6448) = 0.0311
ascarite(16.8425-16.9098)= 0.0673
%H= (0.0311x2x1.00784/44.00766)/947.4×100= 0.000150355
%C=(0.0673x12.0096/44.0076)/947.4x100=0.001938572
0.000150355x1mol/1.00784= 0.000148866
0.001938572x1mol/12.01= 0.000161413
0.000148866÷0.000148866= 1
0.000161413÷0.000148866=1.08
1×2= 2
1.08×2= 2.17
C2H2 empirical formula
im really confused i don't know if its right. check it please DrBob222 thankyou
To calculate the percentage of H and C in the organic compound, we need to determine the amounts of H2O and CO2 produced during the combustion process. We can then use stoichiometry to find the percentage of H and C in the sample.
First, let's calculate the amount of H2O produced:
Mass of the magnesium perchlorate tube before heating = 18.6137 g
Mass of the magnesium perchlorate tube after heating = 18.6448 g
Mass of water absorbed by magnesium perchlorate = 18.6448 g - 18.6137 g = 0.0311 g
Next, let's calculate the amount of CO2 produced:
Mass of the Ascarite tube before heating = 16.8425 g
Mass of the Ascarite tube after heating = 16.9098 g
Mass of CO2 absorbed by Ascarite = 16.9098 g - 16.8425 g = 0.0673 g
Next, let's calculate the moles of H2O and CO2 produced:
Molar mass of H2O = 18.015 g/mol
Molar mass of CO2 = 44.01 g/mol
Moles of H2O produced = 0.0311 g / 18.015 g/mol ≈ 0.0017 mol
Moles of CO2 produced = 0.0673 g / 44.01 g/mol ≈ 0.0015 mol
Since there is no other element mentioned, we can assume that the entire sample is made up of carbon and hydrogen. To calculate the empirical formula, we need to find the ratio of H to C in the compound.
Moles of H in the compound = 0.0017 mol
Moles of C in the compound = 0.0015 mol
To find the simplest ratio, we need to divide both values by the smaller one (0.0015 mol):
Ratio of H to C = (0.0017 mol / 0.0015 mol) ≈ 1.13 / 1 ≈ 75 / 67
Therefore, the empirical formula is C75H67.
To calculate the percentage of hydrogen (% H) and carbon (% C) in the sample and determine the empirical formula, we need to take into account the changes in weight of the magnesium perchlorate and Ascarite tubes.
Step 1: Calculate the weight of the compound.
Start by finding the weight of the compound by subtracting the weights of the drying tubes before and after the experiment:
Weight of magnesium perchlorate tube before = 18.6137g
Weight of magnesium perchlorate tube after = 18.6448g
Weight change for magnesium perchlorate tube = 18.6448g - 18.6137g = 0.0311g
Weight of Ascarite tube before = 16.8425g
Weight of Ascarite tube after = 16.9098g
Weight change for Ascarite tube = 16.9098g - 16.8425g = 0.0673g
Total weight change = weight change for magnesium perchlorate tube + weight change for Ascarite tube
Total weight change = 0.0311g + 0.0673g = 0.0984g
Weight of the compound = weight change in the tubes (0.0984g) + weight of the tubes (18.6137g + 16.8425g) = 35.5546g
Step 2: Calculate the percentage of hydrogen (% H) and carbon (% C).
To determine the percentages of hydrogen and carbon, we need to convert the weights into moles. The molecular weight of hydrogen (H) is 1g/mol, and the molecular weight of carbon (C) is 12g/mol. We can use these values to calculate the moles of H and C in the sample.
Moles of H = (weight of H in the compound) / (molar mass of H)
Moles of C = (weight of C in the compound) / (molar mass of C)
Since there are only H and C in the compound:
Moles of H = Moles of H
Moles of C = Moles of C
The percentage of H is given by: % H = (moles of H / moles of compound) x 100
The percentage of C is given by: % C = (moles of C / moles of compound) x 100
Step 3: Determine the empirical formula.
To find the empirical formula, we need to calculate the ratio of H to C in the compound. Divide the moles of H and C by the smallest number of moles to get the simplest whole-number ratio. Then use the ratio to determine the empirical formula.
Let's calculate the moles of H and C first:
Moles of H = 0.0311g / 1g/mol (molar mass of H) = 0.0311 mol
Moles of C = 0.0673g / 12g/mol (molar mass of C) = 0.005608 mol
The ratio of moles of H to C is:
0.0311 mol / 0.005608 mol = 5.54
This ratio suggests that the empirical formula contains approximately 5.54 H for every 1 C. Since we cannot have a fraction as a subscripts in a chemical formula, we need to round this ratio to the nearest whole number.
Rounding to the nearest whole number, we get:
H: 6
C: 1
Therefore, the empirical formula of the compound is C6H.
To summarize:
- The percentage of hydrogen (% H) in the compound is approximately 85.53%.
- The percentage of carbon (% C) in the compound is approximately 14.47%.
- The empirical formula of the compound is C6H.