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Sergio039 [100]
3 years ago
5

Calculate the molar mass of a compound from the following information. You find that the freezing point of benzene is 5.5 degree

s C. You then dissolve 1.60 grams of the unknown compound in 20.00 grams of benzene. The freezing point of the solution is found to be 2.8 degrees C. The freezing point depression constant for benzene is 4.3 degrees C/m.
Chemistry
1 answer:
jenyasd209 [6]3 years ago
7 0

Answer:

The molar mass (Mm) of the compound is 127.39 g/mole

Explanation:

ΔT = Kf. molality

ΔT = change in temperature = Tfinal - Tinitial = 2.8 - 5.5

Kf = freezing point depression constant = - 4.3 C/m (always negative because temperature is decreasing)

molality = moles of solute/Kg of solvent = mole (n)/(20 x 10^-3 Kg of benzene)

(2.8 - 5.5) = (-4.3) x molality

molality = 0.6279 mole/kg

0.6279 = mole of compound/(20 x 10^-3)

mole of compound = 0.01256 mole

mole (n) = mass (m) divided by Molar mass (Mm)

Molar mass = mass of compound / mole of compound

m/n = 1.6/0.01256 = 127.39 g/mole

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On a coordinate plane, which single transformation could map point A (3,-4) onto point A' (1.5,-2)? *
Ksenya-84 [330]

Answer: A dilation with rule: (x,y)\to(\dfrac12x,\dfrac12y)

Explanation:

A dilation is a non-rigid transformation that creates an image that is the same shape as the original but has a different size.

It uses a scale factor k such that

(x,y)\to(kx,ky)

(x,y)= coordinates of original figure

(kx,ky) = corresponding coordinate in the image.

To transform: A (3,-4) onto point A' (1.5,-2).

Using scale factor k= \dfrac12, we have

A(3,-4)\to A'(\dfrac12\times3, \dfrac12\times-4)=A'(1.5,-2)

Required rule: (x,y)\to(\dfrac12x,\dfrac12y)

3 0
2 years ago
A student puts 0.020 mol of methyl methanoate into an empty and rigid 1.0 L vessel at 450 K. The pressure is measured to be 0.74
stellarik [79]

Explanation:

Starting moles of ethanol acid = 0.020 mol

At the equilibrium 50 % of the ethanol acid molecules reacted

∴ Moles of ethanol acid reacted = 0.020 mol * 50 %/100 %

                                                                   = 0.010 mol

Moles of ethanol acid remain = 0.020 mol + 0.010 mol = 0.010 mol

Moles of the product (CH3COOH)^{2} gas formed are calculated as

0.010 mol CH3COOH * 1 mol (CH3COOH)^{2} / 2 mol CH3COOH

= 0.005 mol (CH3COOH)^{2}

Therefore at the equilibrium total moles of gas present in the vessel are 0.010 mol CH3COOH and 0.005 mol (CH3COOH)^{2}

That is total gas moles at equilibrium = 0.010 mol + 0.005 mol = 0.015 mol

Now Calculate the pressure  :

0.020 mol gas has pressure of 0.74 atm therefore at the same condition what will be the pressure exerted by 0.015 mol gas

P1/n1 = P2/n2

P2 = P1*n2 / n1

      = 0.74 atm * 0.015 mol / 0.020 mol

     = 0.555 atm

4 0
3 years ago
Calcium reacts with Hydrochloric acid to produce Calcium chloride and
hammer [34]

Answer:

Mass = 2.77 g

Explanation:

Given data:

Mass of HCl = 2 g

Mass of CaCl₂ produced = ?

Solution:

Chemical equation:

2HCl + Ca    →     CaCl₂ + H₂

Number of moles of HCl:

Number of moles = mass / molar mass

Number of moles = 2 g/ 36.5 g/mol

Number of moles = 0.05 mol

now we will compare the moles of HCl with CaCl₂.

                   HCl       :         CaCl₂

                     2         :          1

                   0.05     :       1/2×0.05 = 0.025 mol

Mass of CaCl₂:

Mass = number of moles × molar mass

Mass = 0.025 mol × 110.98 g/mol

Mass = 2.77 g

8 0
3 years ago
How do you determine the volume of a regular object if you don't know the density?
Ann [662]

Answer:

mol times or devided by molar volume

4 0
2 years ago
Question 5 (1 point)
Marianna [84]

Answer:

P=12.16 atm

Explanation:

Using the formula of ideal gas law:

PV = nRT

P= nRT/V

 n= number of moles

 R= Avogadro constant = 0.0821

 T= Temperature in K => ºC + 273.15 K

P= (1.50 moles)(0.0821)( 296.15 K)/ 3.00L

P= 12.15

7 0
3 years ago
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