answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
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 .

You might be interested in
A mixture of gases containing 0.20 mol of SO2 and 0.20 mol of O2 in a 4.0 L flask reacts to form SO3. If the temperature is 25ºC
diamong [38]

Answer : The pressure in the flask after reaction complete is, 2.4 atm

Explanation :

To calculate the pressure in the flask after reaction is complete we are using ideal gas equation.

PV=n_TRT\\\\P=(n_1+n_2)\times \frac{RT}{V}

where,

P = final pressure in the flask = ?

R = gas constant = 0.0821 L.atm/mol.K

T = temperature = 25^oC=273+25=298K

V = volume = 4.0 L

n_1 = moles of SO_2 = 0.20 mol

n_2 = moles of O_2 = 0.20 mol

Now put all the given values in the above expression, we get:

P=(0.20+0.20)mol\times \frac{(0.0821L.atm/mol.K)\times (298K)}{4.0L}

P=2.4atm

Thus, the pressure in the flask after reaction complete is, 2.4 atm

5 0
2 years ago
Draw the structure of a compound with molecular formula c5h12 that exhibits only one kind of proton (all 12 protons are chemical
Sophie [7]
The middle carbon is 4-degree since it is attached to 4 carbons. All other carbons are 1-degree since they are attached to only 1 carbon. 

Hydrogens attached with 1-degree carbon are all same. Hydrogen are often refereed to as protons. No carbon is attached to 4-degree carbon. So all hydrogens in this structure are same.

This structure is called  NeoPentane

4 0
2 years ago
Calculate the amount, in moles, of PO43- present at equilibrium when excess Sr3(PO4)2 is added to 750. mL 1.2 M Sr(NO3)2(aq). As
Crank

Answer:

1.8 × 10⁻¹⁶ mol  

Explanation:

(a) Calculate the solubility of the Sr₃(PO₄)₂

Let s = the solubility of Sr₃(PO₄)₂.

The equation for the equilibrium is

Sr₃(PO₄)₂(s) ⇌ 3Sr²⁺(aq) + 2PO₄³⁻(aq); Ksp = 1.0 × 10⁻³¹

                         1.2 + 3s          2s

K_{sp} =\text{[Sr$^{2+}$]$^{3}$[PO$_{4}^{3-}$]$^{2}$} = (1.2 + 3s)^{3}\times (2s)^{2} =  1.0 \times 10^{-31}\\\text{Assume } 3s \ll 1.2\\1.2^{3} \times 4s^{2} = 1.0 \times 10^{-31}\\6.91s^{2} = 1.0 \times 10^{-31}\\s^{2} = \dfrac{1.0 \times 10^{-31}}{6.91} = 1.45 \times 10^{-32}\\\\s = \sqrt{ 1.45 \times 10^{-32}} = 1.20 \times 10^{-16} \text{ mol/L}\\

(b) Concentration of PO₄³⁻

[PO₄³⁻] = 2s = 2 × 1.20× 10⁻¹⁶ mol·L⁻¹ = 2.41× 10⁻¹⁶ mol·L⁻¹

(c) Moles of PO₄³⁻

Moles = 0.750 L × 2.41 × 10⁻¹⁶ mol·L⁻¹ = 1.8 × 10⁻¹⁶ mol

7 0
2 years ago
How many grams o an ointment base must be added to 45 g o clobetasol (T EMOVAT E) ointment, 0.05% w/w, to change its strength to
saw5 [17]

Answer:

Drug calculation

If we have 45g of clobetasol  = 0.05%w/w

Then what mass in g of clobetasol is in 0.03%w/w = 45 x 0.03/0.05 =27g

It means that 27g of clobetasol must be added to change the drug strength to 0.03% w/w

3 0
2 years ago
Write the balanced Ka and Kb reactions for HSO3- in water. Be sure to include the physical states of each species involved in th
Hunter-Best [27]

Answer:

Ka = [H₃O⁺] [SO₃²⁻] / [HSO₃⁻]

Kb = [OH⁻] [H₂SO₃] / [HSO₃⁻]

Explanation:

An amphoteric substance as HSO₃⁻ is a substance that act as either an acid or a base. When acid:

HSO₃⁻(aq) + H₂O(l) ⇄ H₃O⁺(aq) + SO₃²⁻(aq)

And Ka, the acid dissociation constant is:

<h3>Ka = [H₃O⁺] [SO₃²⁻] / [HSO₃⁻]</h3><h3 />

When base:

HSO₃⁻(aq) + H₂O(l) ⇄ OH⁻(aq) + H₂SO₃(aq)

And kb, base dissociation constant is:

<h3>Kb = [OH⁻] [H₂SO₃] / [HSO₃⁻]</h3>

6 0
1 year ago
Other questions:
  • Rhett is solving the quadratic equation 0= x2 – 2x – 3 using the quadratic formula. Which shows the correct substitution of the
    12·1 answer
  • A 55-g sample of a gaseous fuel mixture contains 0.43 mole fraction propane; the remainder of the mixture is butane. What are th
    14·1 answer
  • Which statement is true? Nuclear power plants require more fuel than conventional power plants. There is a short supply of high
    13·2 answers
  • Which industrial facility is most likely to produce toluene and benzene wastes?
    13·2 answers
  • Question 1(Multiple Choice Worth 3 points)
    13·1 answer
  • Please help!!
    13·1 answer
  • To save time you can approximate the initial volume of water to ±1 mL and the initial mass of the solid to ±1 g. For example, if
    14·1 answer
  • What volume of water should be used to dissolve 19.6 g of LiF to create a 0.320 M solution?
    14·1 answer
  • A diver is going through ocean search-and-rescue training. The graph shows the relationship between her depth and the time in se
    13·1 answer
  • What happens when carbon dioxide is cooled to 780C?<br>Where is carbon dioxide found in nature?​
    9·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!