CHEMISTRY HIGH SCHOOL

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.a. Calculate the molality of the solution.

b. Calculate the molarity of the solution.

c. Calculate the mole fraction of the salt in the solution.

Answers

Answer 1

Answer:

The molarity of the solution is 5.018 mol/L and molality of the solution 5.9846 mol/kg.

Assume 100 g of solution the salt concentration- 35 % and water will be 65 %.

So,

mass of salt = 35 g

mass of water = 65 g

Number of moles,

$\bold {moles = \frac {mass} { molar\ mass}}$

So,

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

moles of water = 65 / 18 = 3.6111 mole

Volume of solution,

$\bold {volume =\frac { mass } {density }}$

volume = 100 g / ( 1.29 g/ml)

volume of solution = 77.52 ml = 0.07752 L

$\bold {Molality = \frac {moles\ of \salt} { mass\ of\ water (kg)}}$

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

mole fraction of salt = moles of salt / total moles

mole fraction of salt = 0.389 mol / ( 0.389 + 3.6111)

mole fraction of salt = 0.09725

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Answer 2

Answer:

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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Which compound has the highest percent composition by mass of strontium?

Answers

Assuming all the compounds of interest are given. We proceed on the theoretical way of answering this question. Assume 1 gram of each compound. Multiply it by the reciprocal of the molar mass of the compound. Then multiply it by the molar ratio of the Strontium to the compound. Then, multiply it by the molar mass of strontium. Finally divide this answer by 1 gram and multiply by 100.

Calculate the number of kilojoules to warm 125 g of iron from 23.5 °C to 78.0 °C.

Answers

Final answer:

Using the formula q = mcΔT, and substituting the values for mass, specific heat capacity of iron, and temperature change, it is calculated that it takes approximately 3.058 KJ to warm 125 g of iron from 23.5 °C to 78.0 °C.

Explanation:

To calculate the amount of heatneeded to warm 125 g of iron from 23.5 °C to 78.0 °C, we use the formula q = mcΔT, where 'm' is the mass in kilograms, 'c' is the specific heat capacity, and 'ΔT' is the temperature change. In this case, the mass 'm' is 0.125 kg (since 1 g = 10^-3 kg), the specific heat capacity 'c' of iron is 0.449 J/g°C (or 449 J/kg°C), and 'ΔT' is 78.0 °C - 23.5 °C = 54.5 °C.

Substituting these values into the formula, we get q = (0.125 kg) * (449 J/kg°C) * (54.5 °C), which gives a result of approximately 3.058 KJ.

Therefore, it would take approximately 3,058 KJ to warm 125 g of iron from 23.5 °C to 78.0 °C.

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Final answer:

To warm 125 g of iron from 23.5 °C to 78.0 °C, it requires approximately 3.93 kilojoules of energy.

Explanation:

To calculate the number of kilojoules required to warm 125 g of iron from 23.5 °C to 78.0 °C, we can use the formula:

q = m * c * ΔT

Where:

q is the energy absorbed or released
m is the mass of the substance
c is the specific heat capacity of the substance
ΔT is the change in temperature

Using the given values:

m = 125 g
c = 0.450 J/g°C (specific heat capacity of iron)
ΔT = 78.0 °C - 23.5 °C

Substituting the values into the formula:

q = 125 g * 0.450 J/g°C * (78.0 °C - 23.5 °C)

Simplifying the equation:

q = 125 * 0.450 * (78.0 - 23.5)

q ≈ 3933.75 J ≈ 3.93 kJ

Therefore, it requires approximately 3.93 kilojoules of energy to warm 125 grams of iron from 23.5 °C to 78.0 °C.

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how many moles are in 9.8 grams of calcium?

Answers

when the number of moles Ca = mass of Ca / molar mass of Ca.

and we can get the molar mass of Ca, it is = 40 g/mol

and we have already the mass of Ca (given) = 9.8 g

so, by substitution: the moles Ca = 9.8 g / 40 g/mol

= 0.245 moles

According to mole concept, there are 0.245 moles in 9.8 grams of calcium.

Mole is defined as the unit of amount of substance . It is the quantity measure of amount of substance of how many elementary particles are present in a given substance.

It is defined as exactly 6.022×10²³ elementary entities. The elementary entity can be a molecule, atom ion depending on the type of substance. Amount of elementary entities in a mole is called as Avogadro's number.

It is widely used in chemistry as a suitable way for expressing amounts of reactants and products.For the practical purposes, mass of one mole of compound in grams is approximately equal to mass of one molecule of compound measured in Daltons. Number of moles=mass/molar mass=9.8/40=0.245 moles.

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Please help me, please

Answers

Answer:

A. Metal

Explanation:

Hope this helps! :)

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Answer:

Metal

Explanation:

they deleted my answer so I am putting it back sorry

Which sequence represents the relationship between pressure and volume of an ideal gas as explained by the kinetic-molecular theory?

Answers

smaller volume > crowded particles > more collisions > higher pressure

Boyle's law which plays a major role in the kinetic-theory states that Volume and Pressure are inversely proportional

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(2) 2.08 s (4) 8.32 s