When paper is burned, the mass of the remaining ash is less than the mass of the original paper.

The principal component of mothballs is naphthalene, a compound with a molecular mass of about 130 amu, containing only carbon a

DIA [1.3K]

Answer:

Empirical formula = C5H4

Molecular formula = C10H8

Explanation:

When the 3000 mg of naphthalene are burned they produce 10.3 mg of CO2. Knowing the unbalanced equation of the combustion of naphthalene, we have:

CxHy + O2 = CO2 + H2O

We calculate the molar composition of the sample. We look for the molecular weights in the periodic table:

CO2 = 12,011 + 2 (15,999) = 44,009 g

Mol C = 10.3 mg * (1 mol CO2 / 44.009 g CO2) * (1 mol C / 1 mol CO2) = 0.234 mmol C

Mass C = 0.234 mmol C * (12.011 g C / 1 mol C) = 2.8105 mg C

Mass H = 3 mg - 2.8105 mg = 0.1895 mg H

Mol H = 0.1895 mg H * (1 mol H / 1,008 g H) = 0.188 mmol H

To calculate the empirical formula, we must divide the number of moles of each element by the smallest number of moles, in this case, of hydrogen:

C = 0.2340 mmol C / 0.1895 mol H = 1.25

H = 0.1895 mmol H / 0.1895 mmol H = 1

We multiply the coefficients by 4, and we have the empirical formula:

C1.25 * 4H1 * 4 = C5H4

The molecular formula is equal to (C5H4)m, where m is calculated by the molecular and empirical mass ratio, as follows:

Empirical mass = (5 * 12.011) + (4 * 1.008) = 64.09 g

m = 130 g / 64.09 g = 2.02 = 2

Therefore we have the molecular formula:

(C5H4)2 = C10H8

4 0

3 years ago

Calculate the vapor pressure of a solution made by dissolving 11.1 g Ca(OH)2 in 1 102 g of water at 25 °C. Vapor pressure of pur

Levart [38]

Answer:

23.15 mmHg.

Explanation:

To solve this question you need to understand that part of Raoult's law in your Chemistry textbook. So, let us delve right into the solution of the question.

We are given parameters such as the mass of Ca(OH)2 to be = 11.1 grams, mass of solvent = 102 grams, the Vapor pressure of pure water= 23.76 mm Hg, temperature = 25°C and vapour pressure of the solution= ??.

The molar mass of Ca(OH)2= 74 g/mol.

The first thing to do is to find the number of moles of Ca(OH)2 and that of water from the formula below;

Mass/ molar mass = Number of moles.

===> Number of moles, n= 11.1/ 74.

Number of moles = 0.15 moles Ca(OH)2.

===> Number of moles, n= 102/ 18.

Number of moles, n= 5.67 moles of water.

Next, we add the two moles together to find the solvent mile fraction since vapour pressure is proportional to mole fraction.

Then;

0.15 + 5.67 = 5.82.

Therefore, 5.67/ 5.82= 0.97.

Hence the vapor pressure of a solution = 0.97 × 23.76.

vapor pressure of a solution = 23.15 mmHg.

4 0

3 years ago

Read 2 more answers

| A solution containing 4.48 ppm KMnO4 exhibits

Artist 52 [7]

Answer:

Molar absorptivity or molar extinction co-effecient = 2120.14 cm⁻¹M⁻¹

Explanation:

First convert Concentration from ppm inM or mol/l

⇒ Molar mass of KMnO₄ = 158.03 g

⇒ 4.48 ppm = 4.48 mg/l = 4.48 x 10⁻³ g/l

⇒ Molarity = $\frac{4.48 X10^{-3} }{158.03X 1(lit)}$ = 2.83 x 10⁻⁵ molar

Absorbance (A) = - log(T) ( T = % transmittance)

= - log(0.859)

= 0.06

According to Lambert Beer's law

ε = $\frac{A}{C X l}$

or, ε = $\frac{0.06}{2.83 X 10^{-5}X1 cm }$

or, ε = 2120.14 cm⁻¹M⁻¹

Where

ε = Molar absorptivity

A = absorbance

C = Molar concentration of KMnO₄ solution

l = length

6 0

3 years ago

What codes for the characteristics of an organism?

Minchanka [31]

B: dna cells should be the answer

5 0

3 years ago

An object has a mass of 5 kg. What force is needed to accelerate it at 6 m/s2? (Formula: F=ma) 0.83 N 1.2 N 11 N 30 N

masya89 [10]

Answer: Option (D) 30N

Detailed Solution:
According to Newton's second law:

F = ma --- (A)

Given:
mass = 5kg
acceleration = 6 m/s^2
F = ?

Plug all the value in equation (A)
F = (5)(6)
Ans: F = 30N

4 0

3 years ago

Read 2 more answers