3. What is the density of a 100 grams (g) box that displaces 20 mL of water?

Phosphoric acid is a triprotic acid ( K a1 = 6.9 × 10 − 3 Ka1=6.9×10−3, K a2 = 6.2 × 10 − 8 Ka2=6.2×10−8, and K a3 = 4.8 × 10 −

irina1246 [14]

Answer: To calculate the pH of the buffer composed of $H_2PO_4^-\text{ and }HPO_4^{-2}$ , we use the $K_a2$

Explanation:

Phosphoric acid is a triprotic acid and it will undergo three dissociation reaction each having their respective dissociation constants.

The chemical equation for the first dissociation reaction follows:

$H_3PO_4\rightleftharpoons H_2PO_4^-+H^+;K_a1=6.9\times 10^{-3}$

The chemical equation for the second dissociation reaction follows:

$H_2PO_4^-\rightleftharpoons HPO_4^{2-}+H^+;K_a2=6.2\times 10^{-8}$

The chemical equation for the third dissociation reaction follows:

$HPO_4^{2-}\rightleftharpoons PO_4^{3-}+H^+;K_a3=4.8\times 10^{-13}$

To form a buffer composed of $H_2PO_4^-\text{ and }HPO_4^{-2}$ , we use the $K_a$ of second dissociation process

To calculate the $pK_a$ , we use the equation:

$pK_a=-\log (K_a)\\\\pK_a=-\log(6.2\times 10^{-8})\\\\pK_a=7.21$

To calculate the pH of buffer, we use the equation given by Henderson Hasselbalch:

$pH=pK_a2+\log(\frac{[\text{conjugate base}]}{[\text{weak acid}]})$

$pH=pK_a2+\log(\frac{[HPO_4^{2-}]}{[H_2PO_4^-]})$

We are given:

$pK_a2$ = negative logarithm of second acid dissociation constant of phosphoric acid = 7.21

$[HPO_4^{2-}]$ = concentration of conjugate base

$[H_2PO_4^{-}]$ = concentration of weak acid

Hence, to calculate the pH of the buffer composed of $H_2PO_4^-\text{ and }HPO_4^{-2}$ , we use the $K_a2$

3 0

4 years ago

A 216-L cylinder holds propane gas at 184.8 kPa of pressure and 127°C. How many moles of propane are in the cylinder?

lbvjy [14]

Answer:

12 moles of propane.

Explanation:

From the question given above, the following data were obtained:

Volume (V) = 216 L

Pressure (P) = 184.8 KPa

Temperature (T) = 127 °C

Number of mole (n) =?

Next, we shall convert 127 °C to Kelvin temperature. This can be obtained as follow:

T(K) = T(°C) + 273

T(°C) = 127 °C

T(K) = 127 + 273

T(K) = 400 K

Finally, we shall determine the number of mole of propane gas in the container. This can be obtained as follow:

Volume (V) = 216 L

Pressure (P) = 184.8 KPa

Temperature (T) = 400 K

Gas constant (R) = 8.314 L.KPa/Kmol

Number of mole (n) =?

PV = nRT

184.8 × 216 = n × 8.314 × 400

39916.8 = n × 3325.6

Divide both side by 3325.6

n = 39916.8 / 3325.6

n = 12 moles

Thus, 12 moles of propane is present in the cylinder

8 0

3 years ago

Which of the following is the most polarizable: F2,H2, C2H6, or all of them?

lukranit [14]

C2H6 is the most polarizable and other two are non-polar molecules

4 0

3 years ago

NH4+H2O →NH3+H3O Which one is acting weaker base?

Nataliya [291]

Answer:

NH3

Explanation:

In solution, they are in equilibrium. NH4+ acts as a bronsted Lowry acid and donates an H to become NH3, and NH3 acts as a bronsted lowry base and accepts an H. In this pair, NH3 is a weak base, which gets its basic character due to the presence of lone pair of nitrogen and its ability to donate it.

8 0

2 years ago

How many liters of HF can be made from 50.0 g of a 12.0M HF solution

aliina [53]

Answer:

Explanation:

The first thing we calculate are the moles: (50.0 g)/(20.0063 g/mol) =2.5 moles

Then we use the inverse formula for the molarity: (2.5 mol)/(12.0 M) = 0.208 L

My bad, I pressed the wrong button for answer!

5 0

3 years ago