There are many legends of the North Star that have been told over the years by different civilizations and of them is a mythical story told about the existence of the star.
What is a Legend of the North Star?It is said that it is a little dot left behind after God created the stars and based on the fact that the dot was not like the other stars as it was almost an afterthought and then it came to the attention of Luminaria who granted the dot its wish and it became a real star like the others and became the Star of Bethlehem.
Hence, it can be seen that the given legend and mythical stories are just one of the many ways humans try to understand the phenomena of astrology and how they attach certain significance to it.
With this in mind, it is very clear to see that the North Star is a special star.
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2. Suppose you are testing the gas in laboratory. If you inserted the burning magnesium ribbon inside the gas jar and magnesium ribbon burnt completely and formed light yellow ash as residue, then which gas was there in the gas jar and what is the name of compound present in yellow ash?
When the magnesium ribbon is burned, it enters the carbon dioxide gas jar and continues to burn. The carbon is left behind as a black soot and extra energy is released as a result of the reaction where the magnesium atoms join the oxygen in the carbon dioxide to form magnesium oxide.
Magnesium ribbon is used in pyrotechnics to ignite thermite reactions or to create certain firework mixes. One of the most popular techniques to start chemical reactions that need a higher temperature to ignite is with magnesium ribbon.The light produced by the burning magnesium ribbon is strong enough to temporarily impair vision. Avert looking at the light source directly. Magnesium combustion in air generates strong heat that can result in burns and start the combustion process in combustible materials.To know more about magnesium ribbon
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what are the limiting and excess reactants when 3.22 moles of Al react with 6.96 moles of HBr
Answer
HBr is the limiting reactant
Al is the excess reactant.
Explanation
Given:
Moles of Al = 3.22 mol
Moles of HBr = 6.96 mol
Equation: 2 Al + 6 HBr → 2 AlBr₃ + 3 H₂
What to find;
The limiting and excess reactants.
Solution:
Note: The limiting reactant is the reactant that is completely used up in a reaction, and thus determines when the reaction stops. While the excess reactant is the opposite.
From the given balanced chemical equation;
2 moles of Al require 6 moles of HBr
Therefore, the given 3.22 moles of Al will require (3.22/2) x 6 = 9.66 moles of HBr
Since the given moles of HBr is 6.96 mol not up to 9.66 moles required, then HBr is the limiting reactant and Al is the excess reactant.
HBr is the limiting reactant
Al is the excess reactant.
Write the correct formula for the following compound:
magnesium hydroxide
The formula of magnesium hydroxide is Mg(OH)2.
How magnesium hydroxide?Magnesium hydroxide is an inorganic compound having the chemical formula of Mg(OH)2. It is present in nature as mineral brucite. It is a white solid substance with low solubility in water. Magnesium hydroxide is a component of antacids such as milk of magnesia. Extended use or overuse of this medication for constipation results in dependence on laxatives and constipation. Overuse of Magnesium hydroxide also causes diarrhea that does not go away, dehydration, and mineral imbalances. Severe nausea, vomiting, or diarrhea are the symptoms of using a high dose of magnesium hydroxide. After using a medicine such as a laxative, nausea, vomiting or diarrhea can be cured.
So we can conclude that Mg(OH)2 is the correct formula for magnesium hydroxide.
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How to balance ____CaCl2 —-> ____Ca+ ____ Cl
In order to properly balance an equation, we need to make sure that the same amount of elements on the reactants side matches the number of elements on the products side, we can do that by increasing the number in front of each molecule, the so called stoichiometric coefficient. In the reaction from the question we can properly balance by adding the following stoichiometric coefficients
For this question we have:
CaCl2 -> Ca + 2 Cl
Definition: This is a type of element or substance that is not a metal.Example: oxygen, nitrogen, hydrogen
This elements or substances that are not a metal are called non-metals.
I think that the answer is Non-metal
Part II Dilution Problems: 17. 350.0 mL of water was added to a 2.3 L solution of NaCl. If the final concentration of the solution was 0.967 M, what was the original concentration of the solution?
ANSWER
The original concentration of the solution is 0.147 mol
EXPLANATION
Given that;
The volume of water is 350.0mL
The volume of NaCl solution is 2.3L
The final concentration of the solution is 0.967M
To find the original concentration of the solution, follow the steps below
Step1: Write the dilution formula
[tex]\text{ M1V1}=M2V2[/tex]Where
• M1 is the original concentration of the solution
,• V1 is the original volume of the of the solution
,• M2 is the final concentration of the solution
,• V2 is the final volume of the solution
Step 2: Convert the volume of water to L
Recall, that 1mL is equivalent to 0.001L
[tex]\begin{gathered} \text{ The volume can be converted below as} \\ \text{ 1mL }\rightarrow\text{ 0.001L} \\ \text{ 350mL }\rightarrow\text{ vL} \\ \text{ Cross multiply} \\ \text{ vL}\times\text{ 1mL }=\text{ 350mL}\times0.001L \\ \text{ Isolate v} \\ \text{ v }=\text{ }\frac{350\cancel{mL}\times\text{ 0.001L}}{1\cancel{mL}} \\ \text{ v }=\text{ 350}\times\text{ 0.001} \\ \text{ v }=\text{ 0.35L} \end{gathered}[/tex]Step 3; Find the original concentration of the solution by substituting by the given data into the formula in step 1
[tex]\begin{gathered} \text{ M1}\times2.3\text{ }=\text{ 0.35}\times\text{ 0.967} \\ \text{ 2.3M1 }=\text{ 0.33845} \\ \text{ Divide both sides by 2.3} \\ \text{ }\frac{2.3M1}{2.3}\text{ }=\text{ }\frac{0.33845}{2.3} \\ \text{ M1}=\text{ 0.147 mol} \end{gathered}[/tex]Hence, the original concentration of the solution is 0.147 mol
A chicken egg has mass 60g. It's shell makes up 10% of the whole egg. The shell is made of Calcium Carbonate; CaCO3. What is the mass of the Ca/ Calcium in the egg shell?
A photon has a frequency of 3.16 * 10^7 Hz. Calculate its energy
If the photon has a frequency of 3.16 × 10 ⁷ Hz, then the energy of the the photon as per Planck's law would be 1.978× 10⁻²⁶ Joules
What is Wavelength?It can be understood in terms of the distance between any two similar successive points across any wave.
C = λν
As given in the problem we have to calculate the energy of the light if the frequency of light is 3.16 × 10 ⁷ Hz
The energy of the photon = h ν
= 6.26 × 10⁻³⁴ × 3.16 × 10 ⁷
= 1.978× 10⁻²⁶ Joules
Thus, If the photon has a frequency of 3.16 × 10 ⁷ Hz, then the energy of the the photon as per Planck's law would be 1.978× 10⁻²⁶ Joules.
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determine the number of significant figures in each of the following numbers.1.) 32.05 =2.) 36541 =3.) 300,012,345 =4.) 36,000 =5.) 100 =6.) 100.0 =7.) 1,0000 =8.)250 =9.) 250. =10.) 407 =
we are required to determine the significant figures in each of the numbers.
1) 4 significant figures
2) 5 significant figures
3) 9 significant figures
4) 5 significant figures
5) 3 significant figures
6) 4 significant figures
7) 5 significant figures
8) 3 significant figures
9) 3 significant figures
10) 3 significant figures
If a volcano erupts and ejects 12.5 moles of sulfur into the atmosphere how many atoms of sulfur is this
In this question, we have to find the number of atoms in 12.5 moles of Sulfur, and the way to do it is by using the Avogadro's number, which is 6.02*10^23 atoms, this value represents how many atoms we have in 1 single mol of any element. Therefore in 12.5 moles we will have:
1 mol = 6.02*10^23 atoms
12.5 moles = x atoms
x = 7.52*10^24 atoms of Sulfur in 12.5 moles
How many grams of MgO are produced when 40.0 grams of O2 react completely with Mg? I picked B but I’m not sure if I’m correct
Step 1
The reaction provided:
2 Mg (s) + O2 (g) => 2 MgO (s) (completed and balanced)
-----------
Step 2
Information provided:
40.0 g of O2 which react completely
---
Information needed:
The molar masses of:
O2) 32.0 g/mol
MgO) 40.3 g/mol
-----------
Step 3
By stoichiometry,
2 Mg (s) + O2 (g) => 2 MgO (s)
32.0 g O2 ------- 2 x 40.3 g MgO
40.0 g O2 ------- X
X = 40.0 g O2 x 2 x 40.3 g MgO/32.0 g O2
X = 101 g MgO
Answer: C 101 g
When 29.0 g of butane reacts with oxygen, 88.0 g of carbon dioxide and 45.0 g of water are produced. What mass of oxygen reacted with the butane?
We need to first write the balanced equation:
[tex]2C_4H_{10}+13O_2\rightarrow8CO_2+10H_2O[/tex]we are given the following:
mass of butane = 29.0 g
mass of carbon = 88.0 g
mass of water = 45.0 g
We want the mass of O2 that reacted.
C4H10 is the limiting reactant, and we know the masses of products produced. We can use that to find out how much oxygen reacted.
We can use CO2:
number of moles of CO2 = 88.0/44.01 = 1.9995 mol
The molar ratio between O2 and CO2 is 13:8
Therefore the number of moles of O2 = 1.9995 x (13/8) = 3.249 mol
Now that we have the number of moles, we can calculate the mass.
m = n x M
m = 3.249 mol x 31.998 g/mol
m = 103.97 g
I get 11 pls help and see if I’m right
Answer
None of these
Explanation
The option for 2-bromo-5propylbenzaldehyde does not seem to be provided
Given the equation below, how many moles of nitrogen gas (N2) areneeded to react with 7.5 moles of hydrogen gas (H2)?N2+ 3H2 —>2 NH3
Answer
2.5 moles of N₂ are needed to react with 7.5 moles of hydrogen gas
Explanation
Given:
Equation: N₂ + 3H₂ → 2NH₃
Moles of H₂ = 7.5 moles
What to find:
The moles of nitrogen gas (N₂) needed to react with 7.5 moles of hydrogen gas
Step-by-step solution:
Let the mole of N₂ needed be x.
From the given balanced chemical equation:
3 moles of H₂ react with 1 mole of N₂
Therefore, 7. 5 moles of H₂ will react with x moles of N₂
Cross multiply
[tex]\begin{gathered} x\text{ moles }N_2\times3\text{ moles H}_2=7.5\text{ moles H}_2\times1\text{ mole N}_2 \\ \text{Divide both sides by 3 moles H}_2 \\ \frac{x\text{ moles }N_2\times3\text{ moles H}_2}{3\text{ moles H}_2}=\frac{7.5\text{ moles H}_2\times1\text{ mole N}_{2}}{3\text{ moles H}_2} \\ x\text{ moles }N_2=2.5\text{ moles} \end{gathered}[/tex]UESTION 14nsider the compound XF. Which of the following is true about the compound?A. If XF is covalent, X could be a metal.B. If XF is ionic, X could be a nonmetal.C. If XF is covalent, the name uses prefixes.D. If XF is covalent, X has a charge of +1.QUESTION 15What are the values of x and y in the compound Agx(CO3)y?O AX= 1, y = 2B. x = 3, y = 1OC. x = 3, y = 2O D.X = 2, y = 1
a. If XF is covalent, X couldn't be a metal. Because covalent bonding occurs between nonmetals. So this alternative is False.
b. If XF is ionic, X could be a nonmetal. Also False. Ionic bonding occurs between a metal and a nonmetal. In this case, we already have a nonmetal, which is F.
c. If XF is covalent, the name uses prefixes. True. When we have a covalent compound, the name of the nonmetal on the left has a prefix indicating the number of atoms of it.
d. If XF is covalent, X has a charge of +1. False. This would happen if it was ionic.
Answer: Alternative "C"
What is the total pressure in kPa exerted by a mixture containing two gases if the partial pressure of one gas is 64 kPa and the partial pressure of the other gas is 50.8 kPa?
Dalton's Law or Law of Partial Pressures says that the total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas that composes it. The partial pressure of a gas on the other hand is defined as the pressure it would exert if it were alone in the container.
So we need to sum all the values:
64 + 50.8 = 114.8 kPa
Answer: 114.8 kPa
How many liters of oxygen gas at STP are required to react with 30.25 g of aluminum in the production of aluminum oxide?
Answer:
18.82L of oxygen gas are needed.
Explanation:
1st) It is necessary to write and balance the chemical reaction:
[tex]3O_2+4Al\rightarrow2Al_2O_3[/tex]2nd) From the balanced reaction, we can see that 3 moles of oxygen gas (O2) react with 4 moles of aluminum (Al). To convert moles to grams, it is necessary to use the molar mass of oxygen (32g/mol) and aluminum (27g/mol):
- O2 conversion:
[tex]\begin{gathered} 1mol-32g \\ 3mol-x=\frac{3mol*32g}{1mol} \\ x=96g \end{gathered}[/tex]- Al conversion:
[tex]\begin{gathered} 1mol-27g \\ 4mol-x=\frac{4mol*27g}{1mol} \\ x=108g \end{gathered}[/tex]Now we can see that 96g of O2 react with 108g of Al.
3rd) We have to calculate the grams of O2 that will react with 30.25g of Al:
[tex]\begin{gathered} 108gAl-96gO_2 \\ 30.25gAl-x=\frac{30.25gAl*96gO_2}{108gAl} \\ x=26.89gO_2 \end{gathered}[/tex]Using the molar mass of oxygen, we know that 26.89g represent 0.84 moles of O2.
4th) Finally, a mole of a gas at STP conditions occupies a volume of 22.4L. With this number and the moles of oxygen gas, we can calculate the liters:
[tex]\begin{gathered} 1mol-22.4L \\ 0.84mol-x=\frac{0.84mol*22.4L}{1mol} \\ x=18.82L \end{gathered}[/tex]So, 18.82L of oxygen gas are needed.
What is the maximum number of electrons that can occupy the n = 2 shell?
Explanation:
If n = 2 we have this posibility:
This shell contains 2 subshells: s and p
Subshell 2s can only contain 2 electrons
Subshell 2p can only contain 6 electrons
Answer: In total, we can have 8 electrons in n = 2
how does a catalyst increase the rate of a reaction?
Answer:
Reducing the activation energy and providing an alternative reaction pathway for the reaction to happen
Explanation:
A lower activation energy means that reactants will need less energy to successfully react to make products, meaning that more successful collisions will happen between reactants, increasing the rate of reaction
A catalyst reduces the activation energy of the reaction, speeding it up. By decreasing the activation energy, the energy hurdle that must be cleared for a chemical reaction to take place, catalysts improve the efficiency of this process.
What is catalyst ?By decreasing the activation energy, the energy hurdle that must be cleared for a chemical reaction to take place, catalysts improve the efficiency of this process.
As a result, catalysts facilitate the formation of chemical bonds between atoms to create novel combinations and new compounds.
A catalyst is a chemical that may be included in a reaction to speed up the process without being consumed. Typically, catalysts shorten the activation energy of a process or alter its mechanism. Proteins called enzymes serve as catalysts in biological processes.
Thus, the catalyst reduces the activation energy of the reaction, speeding it up
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Calculate the frequency and the energy of blue light that has a wavelength of 423 nm (Note => 423 nm = 4.23 * 10^7 m)
According to the Planck's equation,the energy and frequency of blue light are 4.699×10[tex]^-19[/tex] J and 2.363×10⁶ m[tex]^-1[/tex] respectively.
What is Planck's equation?Max Planck discovered the theory which stated that energy is transferred in the form of discrete packs which are called quanta and thus proposed an equation called the Planck's equation which relates energy and frequency of a photon and is given as, E=hcυ or in terms of wavelength it is ,E=hc/λ.
The equation makes use of a constant which is called the Planck's constant and it's value is 6.626×10[tex]^-34[/tex] Js.
In the given problem, energy is calculated as,E=6.626×10[tex]^-34[/tex]×3×10⁸/4.23×10[tex]^-7[/tex]=4.699×10[tex]^-19[/tex] J.
The frequency of light is calculated as follows,4.699×10[tex]^-19[/tex]/19.878×10[tex]^-26[/tex]=2.363×10⁶ m[tex]^-1[/tex].
Thus , the energy and frequency of blue light are 4.699×10[tex]^-19[/tex] J and 2.363×10⁶ m[tex]^-1[/tex] respectively.
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What is the number of formula units in a 9.21 mol sample of CaO ?
Answer:
5.546262 x 10^24 formula units
Explanation:
Use avogadro's number
9.21 mol CaO ((6.022 x 10^23 formula units CaO)/1 mol CaO)) = 5.546 x 10^24.
I rounded to 3 sig figs.
A 5.325-gram sample of methyl benzoate, a compound used in the manufacture of perfumes, is found to contain 3.758 g carbon, .316 g hydrogen, and 1.251 grams of oxygen. What is the empirical formula for this substance?
Answer
The empirical formula for the compound is C₄H₄O₁Explanation
Given:
Mass composition: 3.758 g carbon, 0.316 g hydrogen, and 1.251 grams oxygen.
What to find:
The empirical formula for the substance.
Step-by-step solution:
The first step is to convert the number of grams of each element into moles as shown below using the molar masses of H = 1.00784 g/mol and C = 12.011 g/mol and O = 15.999 g/mol
Note: Mole = Mass/Molar mass
Moles C = 3.758g/12.011 g/mol = 0.31 mol
Moles H = 0.316g/1.00784 g/mol = 0.31 mol
Moles O = 1.251g/15.999 g/mol = 0.078 mol
Now, let's divide the number of moles of each element by the smallest number obtained:
C = 0.31/0.078 = 4
H = 0.31/0.078 = 4
O = 0.078/0.078 = 1
The empirical formula for the compound is C₄H₄O₁
Which of the following best describes what happens when salt dissolves in water?A.) The polar solvent molecules surround the positive sodium ions.B.) The polar solvent molecules surround the positive sodium ions and the negativechloride ions.C.) The solute and solvent molecules form a crystalline structure.D.) The solute and solvent molecules do not interact.
When salt dissolves in water, dissociation occurs. This dissociation forms two ions, one positive and one negative. Water is polar and its molecules has poles negatives and positives. So positive poles of water will surround the negative ions. While negative poles will surround the positive ions.
Answer: Alternative "B"
Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of fluoride ions after the addition of 10.00 mL of 0.0100 M HCl to 25.0 mL of this solution is ________ M.
The concentration of fluoride ions after the addition of 10.00 mL of 0.0100 M HCl to 25.0 mL of this solution is 0.009 M
One of the terms for concentration that is used frequently in solutions would be molarity. It would be explained as the number of moles of solute in one liter of solution.
Molarity can be determined by the formula:
Molarity = moles of solute/ volume of solution
Moles of the HCl can be determined by using the formula:
Moles of solute = molarity × volume of the solution.......(i)
It is given that,
Molarity = 0.0100 M.
Volume = 10.0 mL .
Put the value of given data in above equation:
Moles of solute = (0.0100 M) × (10.0 mL) ×([tex]10^{-3}[/tex]/1 mL)
Moles of solute = [tex]10^{-7}[/tex] M
Now, determine moles of HF.
Moles of solute = (0.126 M) × (25 mL) ×([tex]10^{-3}[/tex]/1 mL)
Moles of solute = 0.00315 M
Total moles = 0.00315 M + 0.0000001 M =0.0031501 M
Total volume = 10.00 mL + 25 mL = 35 mL.
Molarity can be determined by the formula:
Molarity = moles of solute/ volume of solution
Molarity = 0.0031501 M / 35 (1/[tex]10^{-3}[/tex])
Molarity = 0.009 M
Therefore, molarity will be 0.009 M.
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Which temperature is unattainable?
a)_1k
b)_1°C
c)_1°F
d)All of these
Answer:
A is the correct answer.
Explanation:
It is possible to reach 1°C and 1°F because they are both units of temperature. But 1k is not a unit of temperature.
How many moles of H2 is needed to produce 12 moles of NH3
The balanced reaction is:
[tex]N_2+3H_2\rightarrow2NH_3[/tex]According to this, 3 moles of H2 produce 2 moles of NH3. Use this ratio to find the number of moles of NH3 produced:
[tex]12molNH_3\cdot\frac{3molH_2}{2molNH_3}=18molH_2[/tex]It means that 18 moles of H2 are needed to produce 12 moles of NH3
Monica works in a crime lab. Her supervisor tells her that she needs to better understand Locard’s Exchange Principle. How will she MOST accurately demonstrate her understanding of this concept?
A.
She will always test for the presence of blood at crime scenes.
B.
She will use both fingerprints and bullet matching to solve crimes.
C.
She will keep evidence separated so it doesn’t get contaminated.
D.
She will exchange information openly with other crime investigators.
She will keep evidence separated so it doesn’t get contaminated demonstrates the understanding of Locard’s Exchange Principle and is denoted as option C.
What is Locard’s Exchange Principle?This principle states that an individual who commits a crime will bring something into the crime scene and leave with something from it. This also explains that they can be used as evidence during investigation by the appropriate authorities.
Since we are aware that new substances are always brought into and carried away from the crime scene then it is best to keep the evidence separated so it doesn’t get contaminated.
This ensures that the results gotten from the analysis and investigation are accurate and is therefore the reason why option C was chosen as the correct choice.
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The energy released when a nucleus forms is calledQuestion 26 options: enthalpy. atomic mass. a becquerel. binding energy.
The correct answer in this case is binding energy, which is the energy released when a collection of nucleons form a nucleus.
The correct answer is the last choice.
After conditions changed to a volume of a sample of helium at 15.56 mL, 138.7°C and 334.6 kPa. What was its initial volyme at 63.2 °C and 57.3 kPa?O a. 74.2O b. 41.4O c. 2.18O d. 111
Answer
a. 74.2
Explanation
Given that:
The initial temperature, T₁ = 63.2 °C + 273 = 336.2 K
Initial pressure, P₁ = 57.3 kPa
The final volume, V₂ = 15.56 mL
Final temperature, T₂ = 138.7°C + 273 = 411.7 K
Final pressure, P₂ = 334.6 kPa
What to find:
The initial volume, V₁.
Step-by-step solution:
The initial volume, V₁ can be calculated using the combined gas law equation.
[tex]\begin{gathered} \frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2} \\ \\ V_1=\frac{P_2V_2T_1}{P_1T_2}=\frac{334.6kPa\times15.56mL\times336.2K}{57.3kPa\times411.7K} \\ \\ V_1=\frac{1750383.611\text{ }mL}{23590.41}=74.2\text{ }mL \end{gathered}[/tex]Hence, its initial volume at 63.2 °C and 57.3 kPa is 74.2 mL
What is the mass of 9.50 moles of magnesium chloride, MgCl2 ?'