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3 years ago

Why do we need to standardize EDTA in determination of water hardness?

1 answer:

3 0

Standardized means that a specific amount EDTA is added to a specific volume of distilled water. Water hardness is determined by the the amount of a standard EDTA solution to change the color of the water from red to blue. For example if one added the correct amount of EDTA to twice the volume of distilled water the solution would be weak. Titration of the hard water would give a erroneous high result.

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A mixture of gases with a pressure of 800.0 mm hg contains 60% nitrogen and 40% oxygen by volume. What is the partial pressure o

larisa86 [58]

Answer:

The partial pressure of oxygen in the mixture is 320.0 mm Hg

Explanation:

1) Take a base of 100 liters of mixture:

N: 60% × 100 liter = 60 liter

O: 40 % × 100 liter = 40 liter.

2) Volume fraction:

At constant pressure and temperature, the volume of a gas is proportional to the number of molecules.

Then, the mole ratio is equal to the volume ratio. Callin n₁ and n₂, the number of moles of nitrogen and oxygen, respectively, and V₁, V₂ the volume of the respective gases you can set the proportion:

V₁ / V₂ = n₁ / n₂

That means that the mole ratio is equal to the volume ratio, and the mole fraction is equal to the volume fraction.

Then, since the law of partial pressures of gases states that the partial pressure of each gas is equal to the mole fraction of the gas multiplied by the total pressure, you can draw the conclusion that the partial pressure of each gas is equal to the volume fraction of the gas in the mixture multiplied by the total pressure.

Then calculate the volume fractions:

Volume fraction of a gas = volume of the gas / volume of the mixture

N: 60 liter / 100 liter = 0.6 liter

V: 40 liter / 100 liter = 0.4 liter

3) Partial pressures:

These are the final calculations and results:

Partial pressure = volume fraction × total pressure

Partial pressure of N = 0.6 × 800.0 mm Hg = 480.0 mm Hg

Partial pressure of O = 0.4 × 800.0 mm Hg = 320.0 mm Hg

8 0

3 years ago

I need the answer to 452 of arogon

yaroslaw [1]

I'm confused... is there more info?

3 0

3 years ago

What is the theoretical yield if 35.5g of Al reacts 39.0g of Cl2

atroni [7]

Answer : The correct answer for the Theoretical Yield is 48.93 g of product .

Theoretical yield : It is amount of product produced by limiting reagent . It is smallest product yield of product formed .

Following are the steps to find theoretical yield .

Step 1) : Write a balanced reaction between Al and Cl₂ .

2 Al + 3 Cl₂→ 2 AlCl₃

Step 2: To find amount of product (AlCl₃) formed by Al .

Following are the sub steps to calculate amount of AlCl₃ formed :

a) To calculate mole of Al :

Given : Mass of Al = 35.5 g

Mole can be calculate by following formula :

$Mole = \frac{given mass (g)}{atomic mass \frac{g}{mol}}$

$Mole = \frac{35.5 g }{26.9 \frac{g}{mol}}$

Mole = 1.32 mol

b) To find mole ratio of AlCl₃ : Al

Mole ratio is calculated from balanced reaction .

Mole of Al in balanced reaction = 2

Mole of AlCl₃ in balanced reaction = 2.

Hence mole ratio of AlC; l₃ : Al = 2:2

c) To find mole of AlCl₃ formed :

$Mole of AlCl_3 = Mole of Al * Mole ratio$

$Mole of AlCl_3 = 1.32 mol of Al * \frac{2}{2}$

Mole of AlCl₃ = 1.32 mol

d) To find mass of AlCl₃

Molar mass of AlCl₃ = $133.34 \frac{g}{mol}$

Mass of AlCl3 can be calculated using mole formula as:

$1.32 mol of AlCl_3 = \frac{ mass (g)}{133.34 \frac{g}{mol}}$

Multiplying both side by $133.34 \frac{g}{mol}$

$1.32 mole * 133.34\frac{g}{mol} = \frac{mass (g)}{133.34\frac{g}{mol}} *133.34 \frac{g}{mol}$

Mass of AlCl₃ = 176.00 g

Hence mass of AlCl₃ produced by Al is 176.00 g

Step 3) To find mass of product (AlCl₃) formed by Cl₂ :

Same steps will be followed to calculate mass of AlCl₃

a) Find mole of Cl₂

$Mole of Cl_2 = \frac{39.0 g}{70.9\frac{g}{mol}}$

Mole of Cl₂ = 0.55 mol

b) Mole ratio of Cl₂ : AlCl₃

Mole of Cl₂ in balanced reaction = 3

Mole of AlCl₃ in balanced reaction = 2

Hence mole ratio of AlCl₃ : Cl₂ = 2 : 3

c) To find mole of AlCl₃

$Mole of AlCl_3 = mole of Cl_2 * mole ratio$

$Mole of AlCl_3 = 0.55 mole * \frac{2}{3}$

Mole of AlCl3 = 0.367 mol

d) To find mass of AlCl₃ :

$0.367 mol of AlCl_3 = \frac{mass (g) }{133.34 \frac{g}{mol}}$

Multiplying both side by

$133.34 \frac{g}{mol}$

$0.367 mol of AlCl_3 * 133.34 \frac{g}{mol} = \frac{mass(g)}{133.34\frac{g}{mol}} * 133.34 \frac{g}{mol}$

Mass of AlCl₃ = 48.93 g

Hence mass of AlCl₃ produced by Cl₂ = 48.93 g

Step 4) To identify limiting reagent and theoretical yield :

Limiting reagent is the reactant which is totally consumed when the reaction is complete . It is identified as the reactant which produces least yield or theoretical yield of product .

The product AlCl₃ formed by Al = 176.00 g

The product AlCl₃ formed by Cl₂ = 48.93 g

Since Cl₂ is producing less amount of product hence it is limiting reagent and 48.93 g will be considered as Theoretical yield .

7 0

3 years ago

Read 2 more answers

How much heat is released when you condense 93.9 g of water vapor? Show work please ❤️

sammy [17]

Answer:

211.9 J

Explanation:

The molecules of water release heat during the transition of water vapor to liquid water, but the temperature of the water does not change with it.

The amount of heat released can be represented by the formula:

$Q=mL_e$

where $Q$ = heat energy, $m$ = mass of water and $L$ = latent heat of evaporation.

The latent heat of evaporation for water is $L=2257 kJ/kg$ and the mass of the water is $m=93.9 g=0.0939 kg$ .

The amount of heat released in this process is:

$Q=mL_e = (0.0939kg)(2257 kJ/kg)=$ 211.9 J

7 0

3 years ago

A molecule has sp2 hybridization with 1 lone pair.... The electron pair geometry of this molecule is: ... The geometry of this m

MrRa [10]

Answer:

The electron pair geometry is Trigonal planar

Molecular geometry - Bent

Approximate bond angle - <120°

Explanation:

The valence shell electron pair repulsion theory enables us to predict the shapes of molecules based on the number of electron pairs present on the valence shell of the central atom and based on the hybridization state of the central atom.

sp2 hybridization corresponds to trigonal planar geometry. Let us recall that the presence of lone pairs causes a deviation of the molecular geometry from the expected geometry based on the number of electron pairs.

Hence, owing to one lone pair present, the observed molecular geometry is bent.

6 0

3 years ago

Why do we need to standardize EDTA in determination of water hardness?​

Why do we need to standardize EDTA in determination of water hardness?