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3 years ago

A solution of salt (molar mass 90 g mol-1) in water has a density of 1.29 g/mL. The concentration of the salt is 35% by mass.

Chemistry

1 answer:

posledela3 years ago

5 0

Answer:

a) 5.9846 mol/kg

b) 5.018 mol/L

c)0.09725

Explanation:

consider 100 g of solution

now

since the salt is 35 % , water will be 65 %

now

mass of salt = 35 g

mass of water = 65 g

we know that

moles = mass / molar mass

moles of salt = 35 g / 90 (g/mol) = 0.389 mol

moles of water = 65 / 18 = 3.6111 mol

now

volume of solution = mass of solution / density of solution

volume of solution = 100 g / ( 1.29 g/ml)

volume of solution = 77.52 ml

volume of solution = 0.07752 L

a)molality = moles of salt / mass of water (kg)

molality = 0.389 mol / 0.065 kg

molality = 5.9846 mol/kg

molarity = moles of salt / volume of solution (L)

molarity = 0.389 mol / 0.07752 L

molarity = 5.018 mol/L

now

total moles in the solution = moles of salt + moles of water

total moles in the solution = 0.389 + 3.6111

total moles in the solution = 4 mol

now

mole fraction of salt = moles of salt / total moles

mole fraction of salt = 0.389 mol / 4 mol

mole fraction of salt = 0.09725

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Potassium (K) having 9 valance electrons can donate a single electron to Fluorine and reach the noble state by completing the Octet.

Option D

<u>Explanation:</u>

Octet Rule:

When the atoms of an element hold 8 independent valance electrons in their outermost orbit; the element converts into its noble state where it doesn't need to react or combine to any other element and gets stable. Each element tend to reach such state by either donating or receiving electrons to satisfy the Octet rule.

Here in this case, we can see that its Potassium which can donate a single electron to Fluorine as it has 19 electrons in each of its atoms. If we see its electronic configuration, we will know that the electrons are divided in three orbits having 2, 8 and 9 electrons, respectively.

Now, if a Potassium atom leaves one of its valence electrons out of 9; the count will be reduced to 8 which will make it stable according to the Octet Rule and hence, it forms a noble gas. Thus, it's Potassium which can donate an electron and gets stable.

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3 years ago

Read 2 more answers

The specific heat capacity of silver is 0.24 J/°C ·g.

kirza4 [7]

Answer:

A) 900 J

B) 27.96 J

C) 1,628 J ≅ 1.63 kJ

Explanation:

The heat absorbed by the metal (silver) - or energy required to heat it - is calculated as:

heat = mass x Cp x ΔT

Where Cp is the heat capacity (0.24 J/°C ·g) and ΔT is the change in temperature (final T - initial T).

A) Given:

mass = 150.0 g

final T = 298 K = 25°C

initial T = 273 K = 0°C

We calculate the energy in J to raise the temperature:

heat = mass x Cp x (final T - initial T)

= 150 .0 g x 0.24 J/°C ·g x (25°C - 0°C )

= 900 J

B) Given:

moles Ag= 1.0 mol

ΔT = 1.08°C

We first calculate the mass of silver (Ag) by multiplying the moles of Ag by the molar mass of Ag (MM = 107.9 g/mol)

mass = moles x MM = 1.0 mol Ag x 107.9 g/mol Ag = 107.9 g

Then, we calculate the heat required:

heat = mass x Cp x ΔT = 107.9 g x 0.24 J/°C ·g x 1.08°C = 27.96 J

C) Given:

heat = 1.25 kJ = 1,250 J

final T = 15.28°C

initial T = 12.08°C

We first calculate the change in temperature:

ΔT = final T - initial T = 15.28°C - 12.08°C = 3.2°C

Then, we calculate the mass of silver:

mass = heat/(Cp x ΔT) = 1,250 J/(0.24 J/°C ·g x 3.2°C) = 1,628 J ≅ 1.63 kJ

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3 years ago

Which is another word for 10 meters in the metric system?

kotegsom [21]

Answer:

Dekameter

Explanation:

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3 years ago

Lavoisier's discovery that air was not a substance but rather a mixture of nitrogen and oxygen is described as history-making. w

Taya2010 [7]

Antoine Lavoisier was part of a wealthy family in Paris. He pursued to study science upon realizing that chemistry or the study of the elements was not a well-studied field. His discovery of that air was a mixture of nitrogen and oxygen gave rise to the concept of COMBUSTION after repeating the experiments made by Priestly using mercury and other metal oxides.

The event was such a history-making because it disproved that concept that air was a pure substance along with 3 others: earth, fire, and water.

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3 years ago

The addition of hydrochloric acid to a silver nitrate solution precipitates silver chloride according to the reaction:

Nimfa-mama [501]

Answer:

Enthalpy change for the reaction is -67716 J/mol.

Explanation:

Number of moles of $AgNO_{3}$ in 50.0 mL of 0.100 M of $AgNO_{3}$

= Number of moles of HCl in 50.0 mL of 0.100 M of HCl

= $\frac{0.100}{1000}\times 50.0$ moles

= 0.00500 moles

According to balanced equation, 1 mol of $AgNO_{3}$ reacts with 1 mol of HCl to form 1 mol of AgCl.

So, 0.00500 moles of $AgNO_{3}$ react with 0.00500 moles of HCl to form 0.00500 moles of AgCl

Total volume of solution = (50.0+50.0) mL = 100.0 mL

So, mass of solution = ( $100.0\times 1.00$ ) g = 100 g

Enthalpy change for the reaction = -(heat released during reaction)/(number of moles of AgCl formed)

= $\frac{-m_{solution}\times C_{solution}\times \Delta T_{solution}}{0.00500mol}$

= $\frac{-100g\times 4.18\frac{J}{g.^{0}\textrm{C}}\times [24.21-23.40]^{0}\textrm{C}}{0.00500mol}$

= -67716 J/mol

[m = mass, c = specific heat capacity, $\Delta T$ = change in temperature and negative sign is included as it is an exothermic reaction]

4 0

3 years ago