Which of the following is a chemical property? A. Boiling point B. Electrical conductivity C. Flammability D. Malleability

What is the molality of an aqueous KCl solution with a mole fraction of KCl, XKCl = 0.175? (The molar mass of KCl = 74.55 g/mol

NARA [144]

Answer:

The molality of the KCl solution is 11.8 molal

Explanation:

Step 1: Data given

Mol fracrion KCl = 0.175

Molar mass KCl = 74.55 g/mol

Molar mass H2O = 18.02 g/mol

Step 2: Calculate mol fraction H2O

mol fraction H2O = 1 - 0.175 = 0.825

Step 3: Calulate mass of H2O

Suppose the total moles = 1.0 mol

Mass H2O = moles H2O * molar mass

Mass H2O = 0.825 * 18.02 g/mol

Mass H2O = 14.87 grams = 0.01487 kg

Step 4: Calculate molality

Molality KCl = 0.175 / 0.01487 kg

Molality KCl = 11.8 molal

The molality of the KCl solution is 11.8 molal

5 0

2 years ago

If 38.5 grams of potassium react with excess oxygen gas, how many grams of potassium oxide can be produced? 4K + O2 yields 2K2O

Lera25 [3.4K]

Answer:

46.40 g.

Explanation:

It is a stichiometric problem.

The balanced equation of the reaction: 4K + O₂ → 2K₂O.

It is clear that 4.0 moles of K reacts with 1.0 mole of oxygen produces 2.0 moles of K₂O.

We should convert the mass of K (38.5 g) into moles using the relation:

<em>n = mass / molar mass,</em>

n = (38.5 g) / (39.098 g/mol) = 0.985 mole.

<em>Using cross multiplication:</em>

4.0 moles of K produces → 2.0 moles of K₂O, from the stichiometry.

0.985 mole of K produces → ??? moles of K₂O.

∴ The number of moles of K₂O produced = (0.985 mole) (2.0 mole) / (4.0 mole) = 0.4925 mole ≅ 0.5 mole.

Now, we can get the mass of K₂O:

∴ mass = n x molar mass = (0.5 mole) (94.2 g/mol) = 46.40 g.

6 0

2 years ago

You wish to construct a buffer of pH=7.0. Which of the following weak acids (w/ corresponding conjugate base) would you select?

Alex17521 [72]

Answer:

C.) HOCl Ka=3.5x10^-8

Explanation:

In order to a construct a buffer of pH= 7.0 we need to find the pKa values of all the acids given below

we Know that

pKa= -log(Ka)

therefore

A) pKa of HClO2 = -log(1.2 x 10^-2)

=1.9208

B) similarly PKa of HF= -log(7.2 x 1 0^-4)= 2.7644

C) pKa of HOCl= -log(3.5 x 1 0^-8)= 7.45

D) pKa of HCN = -log(4 x 1 0^-10)= 9.3979

If we consider the Henderson- Hasselbalch equation for the calculation of the pH of the buffer solution

The weak acid for making the buffer must have a pKa value near to the desired pH of the weak acid.

So, near to value, pH=7.0. , the only option is HOCl whose pKa value is 7.45.

Hence, HOCl will be chosen for buffer construction.

3 0

3 years ago

Having studied the data for patterns and trends, you should now be able to draw

avanturin [10]

Answer:

The situation given here is imaginary such that the life of Rock has to be found using the half-life of the element lokium that has been found inside the rock.

Half-life of any material is the amount of time taken by that particular material to decay. Now the amount of lokium found in rock can show after how many half-lives this amount has been left out.

The time elapsed will be log (L) atoms X half-life.

Explanation:

3 0

2 years ago

Is dynamite an atom or a molecule?

kkurt [141]

Answer:

TNT is a molecule

Explanation:

4 0

2 years ago

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