Ask question

Ask question

All categories

11111nata11111 [884]

3 years ago

9

18 An important environmental consideration is the appropriate disposal of cleaning solvents. An environmental waste treatment c

ompany analysed a cleaning solvent, J, and found it to contain the elements carbon, hydrogen, and chlorine only. The chemical composition of J was determined using different analytical chemistry techniques. Combustion reaction: Combustion of 1.30 g of J gave 0.872 g CO2 and 0.089 g H2O. Precipitation reaction with AgNO3(aq): 0.535 g of J gave 1.75 g AgCl precipitate. (a) Determine the percentage by mass of carbon and hydrogen in J, using the combustion data. (3) (b) Determine the percentage by mass of chlorine in J, using the precipitation data. (1) (c) The molar mass was determined to be 131.38 g mol–1. Deduce the molecular formula of J.

1 answer:

Katyanochek1 [597]3 years ago

5 0

Answer:

a) Percentage by mass of carbon: 18.3%

Percentage by mass of hydrogen: 0.77%

b) Percentage by mass of chlorine: 80.37%

c) Molecular formula: $C_{2} H Cl_{3}$

Explanation:

Firstly, the mass of carbon must be determined by using a conversion factor:

$0.872g CO _{2} *\frac{12g C}{44g CO_{2} } = 0.238g CO_{2}$

The same process is used to calculate the amount of hydrogen:

$0.089g H_{2}O*\frac{2g H}{18g H_{2}O } = 0.010g H$

The percentage by mass of carbon and hydrogen are calculated as follows:

%C $\frac{0.238g}{1.3g} *100%$ = 18.3%

%H $\frac{0.010g}{1.3g} *100%$ =0.77%

From the precipation data it is possible obtain the amount of chlorine present in the compound:

$1.75 AgCl*\frac{35.45g Cl}{143.45g AgCl}$ = 0.43g AgCl

Let's calculate the percentage by mass of chlorine:

%Cl= $\frac{0.43g}{0.535g} * 100%$ = 80.37%

Assuming that we have 100g of the compound, it is possible to determine the number of moles of each element in the compound:

$18.3g C*\frac{1mol C}{12g C} = 1.52mol C$

$0.77g H*\frac{1mol H}{1g H} = 0.77mol H$

$80.37gCl*\frac{1molCl}{35.45g Cl} = 2.27mol Cl$

Dividing each of the quantities above by the smallest (0.77mol), the subscripts in a tentative formula would be

$C=\frac{1.52}{0.77} = 1.97$ ≈ 2

$H = \frac{0.77}{0.77} = 1$

$Cl =\frac{2.27}{0.77}=2.94$ ≈3

The empirical formula for the compound is:

$C_{2} H Cl_{3}$

The mass of this empirical formula is:

mass of C + mass of H + mass of Cl= 24g +1+ 106.35 =131.35g

This mass matches with the molar mass, which means that the supscript in the molecular formula are the same of the empirical one.

You might be interested in

Feliz [49]

Answer:

9

Explanation:

7 0

2 years ago

When 8.0 grams of sodium hydroxide is dissolved in sufficient water to make 400. mL of solution, what is the concentration of th

nata0808 [166]

Answer:

The concentration of this sodiumhydroxide solutions is 0.50 M

Explanation:

Step 1: Data given

Mass of sodium hydroxide (NaOh) = 8.0 grams

Molar mass of sodium hydroxide = 40.0 g/mol

Volume water = 400 mL = 0.400 L

Step 2: Calculate moles NaOH

Moles NaOH = mass NaOH / molar mass NaOH

Moles NaOH = 8.0 grams / 40.0 g/mol

Moles NaOh = 0.20 moles

Step 3: Calculate concentration of the solution

Concentration solution = moles NaOH / volume water

Concentration solution = 0.20 moles / 0.400 L

Concentration solution = 0.50 M

The concentration of this sodiumhydroxide solutions is 0.50 M

6 0

3 years ago

To make 340mL of a 0.4 M solution of Lici, how many mL of a 8 M solution should be used?

ioda

Answer:

Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains. Volume is often quantified numerically using the SI derived unit, the cubic metre.

Explanation:

3 0

2 years ago

A hydrocarbon contains 85.7% carbon and the remainder

Viefleur [7K]

Answer:

CH₂ ; 67.1 %

Explanation:

To determine the empirical formula we need to find what the mole ratio is in whole numbers of the atoms in the compound. To do that we will first need the atomic weights of C and H and then perform our calculation

Assume 100 grams of the compound.

# mol C = 85.7 g / 12.01 g/mol = 7.14 mol

# mol H = 14.3 g / 1.008 g/mol = 14.19 mol

The proportion is 14.9 mol H/ 7.14 mol C = 2 mol H/ 1 mol C

So the empirical formula is CH₂

For the second part we will need to first calculate the theoretical yield for the 12.03 g NaBH₄ reacted and then calculate the percent yield given the 0.295 g B₂H₆ produced.

We need to calculate the moles of NaBH₄ ( M.W = 37.83 g/mol )

1.203 g NaBH₄ / 37.83 g/mol = 0.0318 mol

Theoretical yield from balanced chemical equation:

0.0318 mol NaBH₄ x 1 mol B₂H₆ / mol NaBH₄ = 0.0159 mol B₂H₆

Theoretical mass yield B₂H₆ = 0.0159 mol x 27.66 g/ mol = 0.440 g

% yield = 0.295 g/ 0.440 g x 100 = 67.1 %

6 0

3 years ago

Hydrogen gas is filled in a 224 ml glass container at 0 degree celcius and 1 atmospheric pressure. What are the number of molecu

Step2247 [10]

Answer:

$\boxed{\text{6.02 $\math{\times 10^{21}}$ molecules}}$

Explanation:

A pressure of 1 atm and a temperature of 0 °C is the old definition of STP. Under these conditions, 1 mol of a gas occupies 22.4 L.

1. Calculate the moles of hydrogen.

$n = \text{0.224 L} \times \dfrac{\text{1 mol}}{\text{22.4 L}} = \text{0.0100 mol}$

2. Calculate the number of molecules

$\text{No. of molecules} = \text{0.0100 mol} \times \dfrac{\text{6.022 $\times 10^{23}$ molecules}}{\text{1 mol}}\\\\= \textbf{6.02 $\mathbf{\times 10^{21}}$ molecules}\\\\\text{The sample contains }\boxed{\textbf{6.02 $\mathbf{\times 10^{21}}$ molecules}}$

8 0

3 years ago

Read 2 more answers