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pogonyaev
3 years ago
11

Five examples for physical change

Chemistry
2 answers:
Pachacha [2.7K]3 years ago
6 0

Answer:

Melting an ice cube.

Boiling water.

Chopping wood.

Shredding paper

Crushing a can.

Explanation:

SVETLANKA909090 [29]3 years ago
5 0
Melting of ice
Breaking of glass
Tearing of paper
Breaking of egg
Crystalisation
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You want to prepare 500.0 mL of 1.000 M KNO3 at 20°C, but the lab (and water) temperature is 24°C at the time of preparation. Ho
timama [110]

Explanation:

As per the given data, at a higher temperature, at 24^{o}C, the solution will occupy a larger volume than at 20^{o}C.

Since, density is mass divided by volume and it will decrease at higher temperature.

Also, concentration is number of moles divided by volume and it decreases at higher temperature.

At 20^{o}C, density of water=0.9982071 g/ml  

Therefore, \frac{concentration}{density} will be calculated as follows.

                 = \frac{C_{1}}{d_{1}}

                 = \frac{1.000 mol/L}{0.9982071 g/ml}

                 = 1.0017961 mol/g  

At 24^{o}C, density of water = 0.9972995 g/ml

Since, \frac{concentration}{density} = \frac{C_{2}}{d_{2}}

                           = \frac{C_{2}}{0.9972995}

Also,             \frac{C_{1}}{d_{1}} = \frac{C_{2}}{d_{2}}

so,                   1.0017961 mol/g = \frac{C_{2}}{0.9972995}

                      C_{2} = 1.0017961 \times 0.9972995

                                  = 0.9990907 mol/L

Therefore, in 500 ml, concentration of KNO_{3} present is calculated as follows.

             C_{2} = \frac{concentration}{volume}

               0.9990907 mol/L = \frac{concentration}{0.5 L}  

               concentration = 0.49954537 mol

Hence, mass (m'') = 0.49954537 mol \times 101.1032 g/mol = 50.5056 g       (as molar mass of KNO_{3} = 101.1032 g/mol).

Any object displaces air, so the apparent mass is somewhat reduced, which requires buoyancy correction.

Hence, using Buoyancy correction as follows,

                      m = m''' \times \frac{(1 - \frac{d_{air}}{d_{weights}})}{(1 - \frac{d_{air}}{d})}}

where,          d_{air} = density of air = 0.0012 g/ml

                     d_{weight} = density of callibration weights = 8.0g/ml                      

                     d = density of weighed object

Hence, the true mass will be calculated as follows.

           True mass(m) = 50.5056 \times \frac{(1 - \frac{0.0012}{8.0})}{(1 - (\frac{0.0012}{2.109})}

             true mass(m) = 50.5268 g

                                  = 50.53 g (approx)

Thus, we can conclude that 50.53 g apparent mass of KNO_{3} needs to be measured.

8 0
3 years ago
The melting of ice cubes is an exothermic reaction.<br>true or false​
scoray [572]

Answer:

false

Explanation:

5 0
4 years ago
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A beaker containing 80 grams of lead(ii) nitrate, pb(no3)2, in 100 grams of water has a temperature of 30 ºc. approximately how
sukhopar [10]

Answer:

14 g.

Explanation:

  • From the figure attached:

<em>the solubility of lead(II) nitrate, Pb(NO₃)₂, in 100 grams of water has a temperature of 30ºC is </em><em>(66 g).</em>

When beaker containing 80 grams of lead(II) nitrate, Pb(NO₃)₂, in 100 grams of water has a temperature of 30ºC.

<em>∴ The grams of the salt are undissolved, on the bottom of the beaker are </em><em>(14 g).</em>

4 0
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Which of the following atoms has the largest atomic radius and explain why: potassium, gallium, or germanium.
Leni [432]

Answer:

Potassium

Explanation:

The atom with the largest atomic radius is potassium from the given list.

The atomic radius is taken as half of the inter-nuclear distance between two covalently bonded atoms of non-metallic elements or half of the distance between nuclei in the solid metal state.

Across a period in the periodic table, atomic radii decreases progressively from left to right.

This is due to the progressive increase in the nuclear charge without an attendant increase in the number of electronic shells.

3 0
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A pesticide is used to kill crops in a field. A scientist wants to learn how the pesticide is affecting the plants and animals n
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Answer:

introducing a radioactive tracer into a sample of pesticide

Explanation:

8 0
3 years ago
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