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mixas84 [53]
2 years ago
7

A mysterious white powder could be powdered sugar (C12H22O11), cocaine (C17H21NO4), codeine (C18H21NO3), norfenefrine (C8H11NO2)

, or fructose (C6H12O6). When 82 mg of the powder is dissolved in 1.50 mL of ethanol (d = 0.789 g/cm3, normal freezing point −114.6 ∘C, Kf = 1.99 ∘C/m), the freezing point is lowered to −115.5 ∘C. What is the identity of the white powder?
Chemistry
1 answer:
konstantin123 [22]2 years ago
4 0

Answer: norfenefrine (C_8H_{11}NO_2)

Explanation:

Depression in freezing point is given by:

\Delta T_f=i\times K_f\times m

\Delta T_f=T_f^0-T_f=(-114.6-(-115.5)^0C=0.9^0C = Depression in freezing point

i= vant hoff factor = 1 (for non electrolyte)

K_f = freezing point constant = 1.99^0C/m

m= molality

\Delta T_f=i\times K_f\times \frac{\text{mass of solute}}{\text{molar mass of solute}}\times \text{weight of solvent in kg}}

Weight of solvent (ethanol)= density\times volume=0.789g/cm^3\times 1.50cm^3=1.18g=1.18\times 10^{-3}kg

Molar mass of unknown non electrolyte = M g/mol

Mass of unknown non electrolyte added = 82 mg = 0.082 g (1g=1000mg)

0.9=1\times 1.99\times \frac{0.082g}{M g/mol\times 1.18\times 10^{-3}}kg}

M=154g/mol

The molecular mass of norfenefrine (C_8H_{11}NO_2) is near to 154 and thus the identity of the white powder is norfenefrine .

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Helen [10]
1)we need a balanced equation: CuSO₄ + Zn ---> ZnSO₄ + Cu

2) we need to convert the grams of CuSO₄ to moles using the molar mass. 

molar mass CuSO₄= 63.5 + 32.0 + (4 x 16.0)= 160 g/mol

200.0 g CuSO_4 ( \frac{1 mol}{160 grams} )= 1.25 mol CuSO_4

3) convert moles of CuSO₄ to moles of Cu

1.25 mol CuSO_4 ( \frac{1 mol Cu}{1 mol CuSO_4} )= 1.25 mol Cu

4) convert moles of Cu to grams using it's molar mass.

molar mass Cu= 63.5 g/mol

1.25 mol (\frac{63.5 grams}{1 mol} )= 79.4 grams Cu

I did it step-by-step as the explanation but you can do all of this in one step. 

200.0 g CuSO_4 ( \frac{1 mol CuSO_4}{160 g} ) ( \frac{1 mol Cu}{1 mol CuSO_4} ) ( \frac{63.5 grams}{1 mol Cu} )= 79.4 grams Cu


4 0
2 years ago
If the kinetic energy of a particle is equal to twice its rest mass, what is the velocity of the particle? Determine if relativi
ivann1987 [24]

Answer:

The velocity of the particle is 2 m/s,

Explanation:

Kinetic energy is defined as energy of the body due to its motion. It is given by :

K.E=\frac{1}{2}mv^2

Where :

m = mass of the object

v = velocity of the object

We have , particle with mass m and its kinetic energy is twice its mass.

K.E=2m

2m=\frac{1}{2}mv^2

v^2=\frac{4}{1}

v=2

And unit of velocity are m/s , so the velocity of the particle is 2 m/s.

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Olive oil has a density of 0.92g/ml. How much would 1.0 Liter of olive oil weigh in grams?
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Answer:

9.2x10²g

Explanation:

Data obtained from the question include the following:

Density = 0.92g/ml

Volume = 1L = 1 x 1000 = 1000mL

Mass =..?

Density is simply defined as the mass of the substance per unit volume of the substance. Mathematically it can be represented as:

Density = Mass /volume.

Mass = Density x volume

Mass = 0.92 x 1000

Mass = 9.2x10²g.

Therefore, 1L of olive will weigh 9.2x10²g.

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2 years ago
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Henri becquerel and the curies found out that atoms were not indivisible and indestructible

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