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snow_lady [41]
3 years ago
10

There are 24 g of carbon in a substance with a mass of 30 g. What is the percent carbon by mass for this substance?

Chemistry
1 answer:
mihalych1998 [28]3 years ago
8 0

Answer:

Explanation:

The composition of the vapor in mass percent.

According to Dalton's law,

where  is the partial pressure of the gas j,  is the mole fraction of the gas j in the gas mixture and  is the total pressure.

To know the composition of the vapor we must first calculate the molar fractions of the components of the mixture in the vapor:

→  

 →  

If we consider 1 mole of solution then we will have 0.56 mol of benzene and 0.44 mol of toluene in the vapor. In this way, the number of grams of each component in the vapor will be,

The percentage by mass of each component in the vapor will be,

% benzene = (g benzene / g total) x 100% = (43.7 g / (43.7 g + 40.6 g)) x 100% → % benzene = 51.8 %

% toluene = 100 % - % benzene → % toluene = 41.2%

So, the composition of the vapor in mass percent is 51.8 % benzene and 41.2% toluene.

Why is the composition of the vapor different from the composition of the solution?

The composition of the vapor will be different from that of the solution, since the more volatile compound will have a larger molar fraction in the vapor phase than in the liquid phase.

In a mixture with different volatile components the compound that volatilizes more easily is the one that will have greater capacity to escape from the solution in the form of vapor and, therefore, will be in a greater composition in the vapor above the solution.

We can measure this by means of vapor pressure, which is a measure of the volatility of a substance, that is, the capacity of the substance to pass from a liquid to a gaseous state. In the question, benzene is in greater proportion than toluene in the vapor mixture since it has a higher vapor pressure (94.2 torr) than toluene (28.4 torr).

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aliina [53]
Thank you for posting your question here at brainly. I hope the answer will help you. Feel free to ask more questions.
Equate the gravitational force to the electrostatic force: 

<span>KC²/D² = Gm²/D² → C = m√[G/K] = 7.6√[6.67E-11/9E9] = 6.54E-10 coulombs </span>

<span>Number of electrons N = 6.24E18*C = 4.083E9 electrons</span>

4 0
3 years ago
How many micrograms (ug) are in 3.4 x 10^-5 ounces (oz)
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Answer:

964ug

Explanation:

The problem here involves converting from one unit to another.

 We are to convert from ounces to micrograms.

                                    1ug  = 1 x 10⁻⁶g

                                    1oz  = 28.35g

       

So we first convert to grams from oz then take to ug:

 Solving:

                    1oz  = 28.35g

             3.4 x 10⁻⁵oz  will then give  3.4 x 10⁻⁵ x 28.35 = 9.64  x 10⁻⁴g

So;

                    1 x 10⁻⁶g    = 1ug

          9.64  x 10⁻⁴g will give \frac{9.64 x 10^{-4} }{1 x 10^{-6} }      = 9.64 x 10²ug or 964ug

8 0
2 years ago
The amount ofcalcium present in milk can be determined by adding oxalate to asample and measuring the massof calcium oxalate pre
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<u>Answer:</u> The mass percent of calcium in milk is 0.107 %

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}      .....(1)

Given mass of calcium oxalate = 0.429 g

Molar mass of calcium oxalate = 128.1 g/mol

Putting values in equation 1, we get:

\text{Moles of calcium oxalate}=\frac{0.429g}{128.1g/mol}=0.0033mol

The given chemical equation follows:

Na_2C_2O_4(aq.)+Ca^{2+}(aq.)\rightarrow CaC_2O_4(s)+2Na^+(aq.)

Sodium oxalate is present in excess. So, it is considered as an excess reagent. And, calcium ion is a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

1 mole of calcium oxalate is produced from 1 mole of calcium ion

So, 0.0033 moles of calcium oxalate is produced from = \frac{1}{1}\times 0.0033=0.0033mol of calcium ions

  • Now, calculating the mass of calcium ions by using equation 1, we get:

Moles of calcium ions = 0.0033 moles  

Molar mass of calcium ions = 40 g/mol

Putting values in equation 1, we get:

0.0033mol=\frac{\text{Mass of calcium ions}}{40g/mol}\\\\\text{Mass of calcium ions}=(0.0033mol\times 40g/mol)=0.132g

  • To calculate the mass percentage of calcium ions in milk, we use the equation:

\text{Mass percent of calcium ions}=\frac{\text{Mass of calcium ions}}{\text{Mass of milk}}\times 100

Mass of milk = 125 g

Mass of calcium ions = 0.132 g

Putting values in above equation, we get:

\text{Mass percent of calcium ions}=\frac{0.132g}{125g}\times 100=0.107\%

Hence, the mass percent of calcium in milk is 0.107 %

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