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2 years ago

Which reaction follows the law of conservation of matter?

1 answer:

6 0

It's the law! Matter cannot be created or destroyed in chemical reactions. This is the law of conservation of mass. In every chemical reaction, the same mass of matter must end up in the products as started in the reactants.

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Potassium nitrate has a lattice energy of -163.8 kcal/mol and a heat of hydration of -155.5 kcal/mol.

Brut [27]

Answer:

293.99 g

0.293 Kg

Explanation:

Given data:

Lattice energy of Potassium nitrate (KNO3) = -163.8 kcal/mol

Heat of hydration of KNO3 = -155.5 kcal/mol

Heat to absorb by KNO3 = 101kJ

To find:

Mass of KNO3 to dissolve in water = ?

Solution:

Heat of solution = Hydration energy - Lattice energy

= -155.5 -(-163.8)

= 8.3 kcal/mol

We already know,

1 kcal/mol = 4.184 kJ/mole

Therefore,

= 4.184 kJ/mol x 8.3 kcal/mol

= 34.73 kJ/mol

Now, 34.73 kJ of heat is absorbed when 1 mole of KNO3 is dissolved in water.

For 101 kJ of heat would be

= 101/34.73

= 2.908 moles of KNO3

Molar mass of KNO3 = 101.1 g/mole

Mass of KNO3 = Molar mass x moles

= 101.1 g/mole x 2.908

= 293.99 g

= 0.293 kg

293.99 g potassium nitrate has to dissolve in water to absorb 101 kJ of heat.

4 0

3 years ago

A flashlight battery is hooked to a toy motor, and then the battery and the connections are sprayed with a water-proof coating.

denis-greek [22]

Explanation:

Formula to calculate work done by motor is as follows.

Work done by motor = $mass \times g \times height$

where, g = gravitational constant = 10 $m/s^{2}$

Therefore, work done by motor is as follows.

Work done by motor = $1.00 kg \times 10 m/s^{2} \times 10.0 m$

= 100.0 J

Now, heat lost by water will be calculated as follows.

q = $mC \times \Delta T$

= $g \times 4.184 J/g^{o}C \times 0.024^{o}C$

= 10.0 J

Hence, heat gained by motor = heat lost by water

As, heat gained by motor = 10.0 J

So, change in energy = heat gained - work done

Therefore, change in energy will be calculated as follows.

Change in energy = heat gained - work done

= (10.0 J) - (100.0 J)

= -90.0 J

Thus, we can conclude that change in the energy of the battery contents is -90.0 J.

4 0

2 years ago

This is for a study guide, I can't figure it out!

miskamm [114]

The answer is "D" where the number of collisions per unit area is reduced by one-half. Drawing back on the piston means the volume is increased. The pressure is reduced. There are fewer collisions when the pressure is reduced.

3 0

2 years ago

Under certain conditions Argon gas diffuses at a rate of 3.2 cm per second under the same conditions an unknown gas diffuses at

kozerog [31]

Answer:

20 g/mol

Explanation:

We can use Graham’s Law of diffusion:

The rate of diffusion (r) of a gas is inversely proportional to the square root of its molar mass (M).

$r = \frac{1 }{\sqrt{M}}$