Please help me

coldgirl [10]

Buffers - mixtures of conjugate acid and conjugate base at ±1 pH unit from pH = pKa. Resistant to changes in pH in response to small additions of H+ or OH-. ... Polyprotic acids - dissociation of each H+ can be treated separately if the pKa values are different

3 0

3 years ago

HELP! What is the percent composition of carbon in caffeine (C₈H₁₀N₄O₂)? Show your work

Dominik [7]

Caffeine has the following percent composition: carbon 49.48%, hydrogen 5.19%, oxygen 16.48% and nitrogen 28.85%. Its molecular weight is 194.19 g/mol.

8 0

3 years ago

The osmotic pressure of a saturated solution of strontium sulfate at 25 ∘C∘C is 21 torrtorr. Part A What is the solubility produ

USPshnik [31]

Answer

solubility product = 3.18x 10^-7

Explanation:

We were given the pressure in torr then we need to convert to atm for consistency, ten we have

21torr/760= 0.0276315789 atm

21 Torr = .0276315789 atm

P = i M S T

M = P / iRT

Where p is osmotic pressure

T= temperature= 25C+ 273= 298K

for XY vanthoff factor i = 2

S = 0.0821 L-atm / mol K

M = .0276315789 atm / (2)(0.0821 L atm / K mole)(298 K)

M = 0.000564698046 mol/liters

solubility= 0.000564698046 mol/liters

Ksp = [X+][Y-]

Ksp = X^2

Ksp = [Sr^+2] * [SO4^-2]

Ksp = X^2

Ksp = (0.000564698046)^2

Ksp = 3.18883883 × 10-7

Ksp = 3.18x 10^-7

solubility product = 3.18x 10^-7

Therefore, the solubility product of this salt at 25 ∘C∘C is 3.18x 10^-7

7 0

3 years ago

The monomer of poly(vinyl chloride) has the formula C2H3Cl. If there are 1,565 repeat units in a single chain of the polymer, wh

monitta

Answer:

$\large \boxed{9.780 \times 10^{4}\text{ u}}$

Explanation:

The molecular mass of a monomer unit is:

C₂H₃Cl = 2×12.01 + 3×1.008 + 35.45 = 24.02 + 3.024 + 35.45 = 62.494 u

For 1565 units,

$\text{Molecular mass} = \text{1565 units} \times \dfrac{\text{62.494 u}}{\text{1 unit }} = \mathbf{9.780 \times 10^{4}}\textbf{ u}\\\\\text{The molecular mass of the chain is $\large \boxed{\mathbf{9.780 \times 10^{4}}\textbf{ u}}$}$

8 0

3 years ago

Determine the molar mass of a 0.458-gram sample of gas having a volume of 1.20 l at 287 k and 0.980 atm. group of answer choices

lilavasa [31]

Considering the ideal gas law and the definition of molar mass, the molar mass of the sample of gas is 9.17 $\frac{g}{mol}$ .

<h3>Ideal gas law</h3>

An ideal gas is a theoretical gas that is considered to be composed of randomly moving point particles that do not interact with each other. Gases in general are ideal when they are at high temperatures and low pressures.

The pressure, P, the temperature, T, and the volume, V, of an ideal gas, are related by a simple formula called the ideal gas law:

P×V = n×R×T

where:

P is the gas pressure.
V is the volume that occupies.
T is its temperature.
R is the ideal gas constant. The universal constant of ideal gases R has the same value for all gaseous substances.
n is the number of moles of the gas.

<h3>Definition of molar mass</h3>

The molar mass of substance is a property defined as its mass per unit quantity of substance, in other words, molar mass is the amount of mass that a substance contains in one mole.

<h3>Molar mass of the sample of gas</h3>

In this case you know:

P= 0.980 arm
V= 1.20 L
T= 287 K
R= 0.082 $\frac{atmL}{molK}$
n= ?

Replacing in the ideal gas law:

0.980 atm× 1.20 L= n× 0.082 $\frac{atmL}{molK}$ × 287 K

Solving:

(0.980 atm× 1.20 L)÷ (0.082 $\frac{atmL}{molK}$ × 287 K)= n

<u><em>0.04997 moles= n</em></u>

On the other hand, you know that the<u><em> mass of the sample of gas</em></u> is <u><em>0.458 grams</em></u>. Replacing in the definition of molar mass:

$molar mass=\frac{0.458 grams}{0.04997 moles}$