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3 years ago

What is the standard unit used to measure mass

Chemistry

2 answers:

kicyunya [14]3 years ago

8 0

Kg is usually used standard ly

AlladinOne [14]3 years ago

3 0

The standard International System of Units (SI) unit of mass is the kilogram(kg). The kilogram is 1000 grams (g), first defined in 1795 as one cubic decimeter of water at the melting point of ice.

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An unknown compound, X is thought to have a carboxyl group with a pKa of 2.0 and another ionizable group with a pKa between 5 an

Westkost [7]

Answer:

7.3

Explanation:

By Henderson Hasselbalch equation we can calculate the pH or the pOH of a solution by its pKa. Remember that $pH = -log[H^{+}]$ , and pKa = -logKa. Ka is the equilibrium constant of the acid.

Henderson Hasselbalch equation :

$pH = pKa - log \frac{[HA]}{[A^{-}]}$

Where [HA] is the concentration of the acid, and $[A^{-}]$ is the concentration of the anion which forms the acid.

So, acid X, has two ionic forms, the carboxyl group and the other one. First, we have 0.1 mol/L of the acid, in 100 mL, so the number of moles of X

n1 = (0.1 mol/L)x(0.1 L) = 0.01 mol

When it dissociates, it forms 0.005 mol of the carboxyl group and 0.005 mol of the other group. Assuming same stoichiometry.

Adding NaOH, with 0.1 mol/L and 75 mL, the number of moles of $OH^-$ will be

n2 = (0.1 mol/L)x(0.075 L) = 0.0075 mol

So, the 0.0075 mol of $OH^-$ reacts with 0.005 mol of carboxyl, remaining 0.0025 mol of $OH^-$ , which will react with the 0.005 mol of the other group. So, it will remain 0.0025 mol of the other group.

The final volume of the solution will be 175 mL, but both concentrations (the acid form and ionic form) have the same volume, so we can use the number of mol in the equation.

Note that, the number of moles of the acid form is still 0.01 mol because it doesn't react!

So,

$6.72 = pKa - log \frac{0.01}{0.0025}$

6.72 = pKa - log 4

pKa - log4 = 6.72

pKa = 6.72 + log4

pKa = 6.72 + 0.6

pKa = 7.3

8 0

3 years ago

37.5ml of menthol is dissolved in water to make 456 ml of solution, what is the concentration expressed in volume/volume % of th

Ahat [919]

Answer:

V/V% = 8.2%

Explanation:

Given data:

Volume of methanol = 37.5 mL

Volume of solution = 456 mL

V/V% = ?

Solution:

V/V% = [volume of solute / volume of solution ]×100

V/V% = 37.5 mL / 456 mL × 100

V/V% = 0.08× 100

V/V% = 8.2%

3 0

3 years ago

You try to measure out exactly 5.0 milliliters of water by eye into each of five test tubes. When you go back to check the volum

jeka94

Answer:

The volumes are both, accurate and precise.

Explanation:

In the measurement of a set, precision refers to how much coincidence exists in the measurements of an specific value, as the measurements are close, we can say the volumes are precise.

Accuracy means the agreement that exists between the average of one

large series of measurements and the value of measurement

Media is 4,96 ml and I wanted to measure 5 ml. It is also close.

6 0

3 years ago

What do kinetic and potential energy have in common

adell [148]

Just simply... they both are energy.
Use a bow and arrow as an example:
When you pull back an arrow, potential energy or PE is stored in the string and the limbs of the bow.
When you release the the arrow, energy is being transferred from the bow to the arrow. The arrow now has kinetic energy or KE, this means that the energy is being used by the arrow.

7 0

3 years ago

Which of these relies on a renewable resource to produce energy

mrs_skeptik [129]

D- coal-burning stove is the correct answer

7 0

3 years ago