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kherson [118]
3 years ago
5

When 0.875 g. of magnesium was heated in air, 1.25 g. of magnesium oxide

Chemistry
1 answer:
Ilia_Sergeevich [38]3 years ago
3 0

Answer:

1. What is the coefficient for calcium in the balanced equation?

2 Ca + 5 NaOH → 4 Na + 2 Ca(OH)2

2. The burning of 20.0 g of acetylene (C2H2) produces what mass of carbon dioxide? You must

write the equation, balance it and solve the mass-mass problem.

a. Balanced equation:

2 C2H2 + 5 O2  4 CO2 + 2 H2O

Explanation:

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3. What is the energy of a photon whose frequency is 5.2 x 1015 Hz? Use the equation: E = hxv
anzhelika [568]

Answer:

3. 3.45×10¯¹⁸ J.

4. 1.25×10¹⁵ Hz.

Explanation:

3. Determination of the energy of the photon.

Frequency (v) = 5.2×10¹⁵ Hz

Planck's constant (h) = 6.626×10¯³⁴ Js

Energy (E) =?

The energy of the photon can be obtained by using the following formula:

E = hv

E = 6.626×10¯³⁴ × 5.2×10¹⁵

E = 3.45×10¯¹⁸ J

Thus, the energy of the photon is 3.45×10¯¹⁸ J

4. Determination of the frequency of the radiation.

Wavelength (λ) = 2.4×10¯⁵ cm

Velocity (c) = 3×10⁸ m/s

Frequency (v) =?

Next, we shall convert 2.4×10¯⁵ cm to metre (m). This can be obtained as follow:

100 cm = 1 m

Therefore,

2.4×10¯⁵ cm = 2.4×10¯⁵ cm × 1 m /100 cm

2.4×10¯⁵ cm = 2.4×10¯⁷ m

Thus, 2.4×10¯⁵ cm is equivalent to 2.4×10¯⁷ m

Finally, we shall determine the frequency of the radiation by using the following formula as illustrated below:

Wavelength (λ) = 2.4×10¯⁷ m

Velocity (c) = 3×10⁸ m/s

Frequency (v) =?

v = c / λ

v = 3×10⁸ / 2.4×10¯⁷

v = 1.25×10¹⁵ Hz

Thus, the frequency of the radiation is 1.25×10¹⁵ Hz.

8 0
2 years ago
13. A mixture of MgCO3 and MgCO3.3H2O has a mass of 3.883 g. After heating to drive off all the water the mass is 2.927 g. What
rjkz [21]

Answer:

63.05% of MgCO3.3H2O by mass

Explanation:

<em>of MgCO3.3H2O in the mixture?</em>

The difference in masses after heating the mixture = Mass of water. With the mass of water we can find its moles and the moles and mass of MgCO3.3H2O to find the mass percent as follows:

<em>Mass water:</em>

3.883g - 2.927g = 0.956g water

<em>Moles water -18.01g/mol-</em>

0.956g water * (1mol/18.01g) = 0.05308 moles H2O.

<em>Moles MgCO3.3H2O:</em>

0.05308 moles H2O * (1mol MgCO3.3H2O / 3mol H2O) =

0.01769 moles MgCO3.3H2O

<em>Mass MgCO3.3H2O -Molar mass: 138.3597g/mol-</em>

0.01769 moles MgCO3.3H2O * (138.3597g/mol) = 2.448g MgCO3.3H2O

<em>Mass percent:</em>

2.448g MgCO3.3H2O / 3.883g Mixture * 100 =

<h3>63.05% of MgCO3.3H2O by mass</h3>
6 0
2 years ago
The molecules of a substance must have what characteristics in order to be flexible
Goryan [66]
Answer:
            <span>The molecules of a substance which must have the <u>a</u></span><u>bility to move past one another</u> are said to be flexible.

Explanation:
                   Those substances are said to be flexible which can be bent without breaking. There are many substances which are hard in nature but still can be bent. The hardness of such materials is due to strong interactions between the molecules and the flexibility comes due to their amorphous backbone. Therefore, greater the crystalline level of macromolecules lesser is the flexibility and greater the amorphous character greater is the flexibility and vice versa. Also, the flexibility of polymers is increased by adding plastisizers in it. Plastisizers make the hard polymers flexible by breaking the crosslinkers and enabling the macromolecules to move past one another.

6 0
2 years ago
How many mL are 2.3 mol of CO2 at STP?
kupik [55]

Answer:

0.052mL

Explanation:

1mole of a gas occupy 22.4L.

Therefore, 1 mole of CO2 will also occupy 22.4L.

If 1mole of CO2 occupies 22.4L,

Then 2.3moles of CO2 will occupy = 2.3 x 22.4 = 51.52L

coverting this volume to mL, we simply divide by 1000 as shown below:

51.52/1000 = 0.05152mL = 0.052mL

8 0
3 years ago
Read 2 more answers
25 Points Please Help ASAP!! View Attached Image!! Will Mark Brainliest If All Are Answered!!
KIM [24]

Answer:

Answers in explanation.

Explanation:

30. A (A chemical changes changes the chemical properties)

31. C (rusting is an example of a chemical change

32. B (A reaction requires energy, so some energy will be expelled)

33. B (Color change is an example of a chemical change)

34. A (The law of the conservation of mass: Mass and Energy cannot be created nor destroyed)

8 0
2 years ago
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