Answer:
Na₂CO₃.2H₂O
Explanation:
For the hydrated compound, let us denote is by Na₂CO₃.xH₂O
The unknown is the value of x which is the amount of water of crystallisation.
Given values:
Starting mass of hydrate i.e Na₂CO₃.xH₂O = 4.31g
Mass after heating (Na₂CO₃) = 3.22g
Mass of the water of crystallisation = (4.31-3.22)g = 1.09g
To determine the integer x, we find the number of moles of the anhydrous Na₂CO₃ and that of the water of crystallisation:
Number of moles = 
Molar mass of Na₂CO₃ =[(23x2) + 12 + (16x3)] = 106gmol⁻¹
Molar mass of H₂O = [(1x2) + (16)] = 18gmol⁻¹
Number of moles of Na₂CO₃ = 
= 0.03mole
Number of moles of H₂O = 
= 0.06mole
From the obtained number of moles:
Na₂CO₃ H₂O
0.03 0.06
Simplest
Ratio 0.03/0.03 0.03/0.06
1 2
Therefore, x = 2
Answer:
Polar covalent bond
Explanation:
When the electronegativity difference between two elements A and X is 0.8, the bond AX formed will most likely be a polar covalent bond.
A polar covalent bond is one whose electronegativity difference is between 0.5 and 2.1.
In such a bond type, we have heteronuclear species with one of the species having a higher electronegativity value.
- When electronegativity difference is less than 0.5, a non-polar covalent bond forms.
- If the value is greater than 2.1, an ionic bond will form.
x = 20 long tables
y = 5 round table
Explanation:
We have the following system of equations:
x + y = 25
8x + 6y = 190
From the first equation we have:
x = 25 - y
And we replace x in the second equation:
8(25 - y) + 6y = 190
200 - 8y + 6y = 190
200 - 2y = 190
200 - 190 = 2y
10 = 2y
y = 5
Now we insert the value of y in the next equation:
x = 25 - y
x = 25 - 5
x = 20
Learn more about:
system of equations
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Answer:
Infrared radiation → A) used to detect the location of objects
Microwaves → D) Used in radar and to heat food
Ultraviolet light → C)Given off by very hot objects, such as the sun Heat from warm objects
Visible light → B) All the radiation humans can see, ranging from red to violet
Explanation:
Microwaves have magnetic waves with very long lengths, greater than that of infrared light. These waves are produced through vibrations that produce heat, as the microwave is turned on, which allows the food to be heated. These waves are also used to provide communication on some types of devices.
Infrared radiation is a type of non-ionizing radiation that has a low frequency and therefore cannot be visualized, since it is not within a visible electromagnetic spectrum, having a frequency lower than red. It can be used to detect the licalization of objects and does not pose a health risk.
Ultraviolet radiation is extremely harmful to our body. It is characterized by radiation with very small wavelengths, less than 400nm. This type of radiation can be released by the sun and ultraviolet lamps.
Visible light refers to the simplest form of electromagnetic wave and covers all the radiation that our eyes can see, allowing different colors to be seen in the objects we observe according to the reorganization of atoms and molecules.
