How many moles of oxygen gas occupy 67.2 L of volume at STP?<br> A 0.333<br> B 3.00<br> C 1.00

As a technician in a large pharmaceutical research firm, you need to produce 250. mL of a potassium dihydrogen phosphate buffer

Reika [66]

Answer:

We will need 147.772 mL of KH2PO4 to make this solution

Explanation:

For this case we can give the following equation:

H2PO4 - ⇄ H+ + HPO42-

With following pH- equation:

pH = pKa + log [HPO42-]/[H2PO4-]

7.05 = 7.21 + log [HPO42-]/[H2PO4-]

-0.16 = log [HPO42-]/[H2PO4-]

10^-0.16 = [HPO42-]/[H2PO4-]

0.6918 = [HPO42-]/[H2PO4-]

Let's say the volume of HPO42-= x then the volume of H2PO4- will be 250 mL - x

Since both have a concentration of 1M = 1 mol /L

If we plug this in the equation 0.6918 = [HPO42-]/[H2PO4-]

0.6918 = x / (250 - x)

0.6918*250 - 0.6918x = x

172.95 = 1.6918x

x = 102.228 mL

The volume of HPO42- = 102.228 mL

Then the volume of H2PO4- = 250 - 102.228 = 147.772 mL

To control this we can plug this in the pH equation

7.05 = 7.21 + log [HPO42-]/[H2PO4-]

7.05= 7.21 + log (102.228 / 147.772) = 7.05

We will need 147.772 mL of KH2PO4 to make this solution

3 0

3 years ago

A cube has a height of 8 cm and a mass of 457 g. What is its density?

ZanzabumX [31]

Answer:

the answer is b, 0.89

Explanation:

A cube has a height of 8 cm and a mass of 457 g. What is its density?

a. 233,984 g/cm

b. 0.89g/cm3

c. 1.12 g/cm3

Density = mass/volume

the volume of the cube is 8X8X8=512cm3

the mass is 457 gm

the density is 457/512 = 0.889 gm/cm3

the answer is b, 0.89

3 0

2 years ago

When the following reaction comes to equilibrium, will the concentrations of the reactants or products be greater? Does the answ

Nutka1998 [239]

Answer:

At equilibrium, the concentration of the reactants will be greater than the concentration of the products. This does not depend on the initial concentrations of the reactants and products.

Explanation:

The value of Kc gives us an idea of the extent of the reaction. A big Kc (Kc > 1) means that in the equilibrium there are more products than reactants, and the opposite happens for a small Kc (Kc < 1). The equilibrium is reached no matter what the initial concentrations are.

The value of the equilibrium constant is relatively SMALL; therefore, the concentration of reactants will be GREATER THAN the concentration of products. This result is INDEPENDENT OF the initial concentration of the reactants and products.

4 0

3 years ago

A gravel can be broken down into different kinds of substances by physical processes. No chemical reactions are needed to separa

Vlada [557]

Answer:

MIXTURE

Explanation:

A mixture is a substance composed of a combination of other different substances. These component(s) of a mixture are physically combined, meaning that there is no chemical linkage between the individual components/constituents of a mixture.

This is the case of the gravel described in this question. The components of gravel can be separated using physical means because they are not chemically bonded to one another, hence, no chemical reactions are needed to separate different parts of gravel into pure substances. This makes gravel a MIXTURE.

6 0

3 years ago

Read 2 more answers

How do the metals in group 1 compare with the transition metals?

Nimfa-mama [501]

Answer:

Group 1 metals and transition metals are different from each other, mainly based on the colour of the chemical compounds that they form. The key difference between group 1 metals and transition metals is that the group 1 metals form colourless compounds, whereas the transition metals form colourful compounds.

6 0

3 years ago

Read 2 more answers

How many moles of oxygen gas occupy 67.2 L of volume at STP? A 0.333 B 3.00 C 1.00