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3 years ago

7. What is the potential energy of a rock that has a mass of 100 kg that is sitting on top of a hill 300 m high?

Chemistry

1 answer:

levacccp [35]3 years ago

7 0

Answer:

294000 J or 294 kJ

Explanation:

Potential energy is given by:

$U=mgh$

Where U is potential energy, m is mass, g is acceleration due to gravity, and h is height. Using this equation:

$U=100(9.8)(300)\\U=294000$

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During our phase changes lab, where did we place the thermometer?

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The thermometer must be in contact with the ice/water only

Explanation:

In this experiment in the lab, the aim is to measure the specific latent heat of fusion of water.

The specific latent heat of fusion of a substance is the amount of heat energy required to completely melt a certain amount of the substance, mathematically:

$\lambda = \frac{Q}{m}$

where

Q is the heat supplied to the substance

m is the mass of the substance

In this experiment, the aim is to measure the specific latent heat of fusion of water. In order to do that, a mix of ice/water is heated with a certain amount of heat Q, and then it is evaluated the amount of mass m that undergoes melting.

An important precaution that must be taken in this experiment is that the temperature of the water/ice mixture remains constant and equal to the melting point of ice (otherwise, part of the heat supplied to the mixture is used to increase the temperature of the water, resulting in an inaccurate measure of Q). Therefore, a thermometer must be used to check constantly the temperature, and this thermometer must be placed inside the ice/water mixture only (It should not touch the saucepan, whose temperature can be higher).

So, the correct answer is

in contact with the ice/water only

Learn more about specific heat:

brainly.com/question/3032746

brainly.com/question/4759369

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Elza [17]

Answer: There are $21.08\times 10^{23}$ molecules in 63.00 g of $H_2O$

Explanation:

According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number $6.023\times 10^{23}$ of particles.

To calculate the moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}=\frac{63.00g}{18g/mol}=3.5moles$

1 mole of $H_2O$ contains = $6.023\times 10^{23}$ molecules

Thus 3.5 moles of $H_2O$ contains = $\frac{6.023\times 10^{23}}{1}\times 3.5=21.08\times 10^{23}$ molecules.

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