Any science fair project ideas? Something for 7th or 8th grade level.

Answer:

I'm not an expert at this, but I assume its mercury.

Answer:

Explanation:

Chemicals to produce NH₃ ( ammonia )

1 ) Ammonium chloride ( NH₄Cl )

2 ) Calcium hydroxide  Ca(OH)₂

2NH₄Cl + Ca(OH)₂ = CaCl₂ + 2NH₃ + 2H₂O.

Net Ionic equation

2NH₄⁺ ( aq ) + 2OH⁻ (aq )  = 2NH₃(g)  + 2H₂O .

Answer:

B

Explanation:

Answer:

λ = 5.68×10⁻⁷ m

Explanation:

Given data:

Energy of photon = 3.50 ×10⁻¹⁹ J

Wavelength of photon = ?

Solution:

E = hc/λ

h = planck's constant = 6.63×10⁻³⁴ Js

c = 3×10⁸ m/s

Now we will put the values in formula.

3.50 ×10⁻¹⁹ J =  6.63×10⁻³⁴ Js × 3×10⁸ m/s/ λ

λ =  6.63×10⁻³⁴ Js × 3×10⁸ m/s / 3.50 ×10⁻¹⁹ J

λ =  19.89×10⁻²⁶ J.m / 3.50 ×10⁻¹⁹ J

λ = 5.68×10⁻⁷ m

Answer:

1.1 × 10⁻⁶ M

Explanation:

Step 1: Given and required data

Step 2: Write the balanced equation for the solution reaction of calcium oxalate

CaC₂O₄(s) ⇄ Ca²⁺(aq) + C₂O₄²⁻(aq)

Step 3: Calculate the concentration of the oxalate ion to begin the precipitation of calcium oxalate

We will use the Ksp of calcium oxalate.

Ksp = 2.7 × 10⁻⁹ = [Ca²⁺].[C₂O₄²⁻]

[C₂O₄²⁻] = Ksp / [Ca²⁺]

[C₂O₄²⁻] = 2.7 × 10⁻⁹ / 2.5 × 10⁻³

[C₂O₄²⁻] = 1.1 × 10⁻⁶ M

Kidney stones are the calcareous stones formed in the kidney of the excretory system. The initial concentration of oxalate ion was [tex]1.1 \times 10^{-6} \;\rm M.[/tex]

Concentration is the amount of the substance present in the sample and can be calculated by the solubility constant of the products.

Given,

Concentration of calcium = 2.5mM

The solubility product constant = [tex]2.7 \times 10^{-9}[/tex]

The balanced chemical reaction for calcium oxalate can be written as:

[tex]\rm CaC_{2}O_{4}(s) \leftrightharpoons Ca^{2+}(aq) + C_{2}O_{4}^{2-}(aq)[/tex]

The concentration of oxalate ions by Ksp is calculated as:

[tex]\begin{aligned} [C_{2}O_{4}^{2-}] &= \rm \dfrac {Ksp}{[Ca^{2+}]}\\\\&= \dfrac{2.7 \times 10^{-9}}{2.5 \times 10^{-3}}\\\\&= 1.1 \times 10^{-6}\;\rm M\end{aligned}[/tex]

Therefore, [tex]1.1 \times 10^{-6} \;\rm M[/tex] is the concentration of oxalate ion.

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Answer:

The first option is the correct option

Explanation:

Copper is one of the transition elements which are normally found in the d-block. Generally, transition elements that have low oxidation number/charge usually undergo ionic/electrovalent bonding, while those that have a relatively higher oxidation number/charge usually undergo covalent bonding. Copper has charges ranging from 1+, 2+ or 3+ and thus will normally undergo ionic bonding which involves the gain or loss of electrons to meet the octet rule.

The best description of how atoms bond in a copper sample is; the atoms share electrons in order to achieve a stable octet - a type of bonding called Metallic bonding.

According to the question;

Definition:

A metallic bond is pretty different from covalent and ionic bonds, but the objective of the bonding is the same: to achieve a lower energy state.

Contrary to a bond between just two atoms, a metallic bond is a sharing of electrons between many atoms of a metal element.

P.S: Copper is one of the transition metals with variable oxidation states.

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Answer:

C

Explanation:

CO2 is a molecule because it is compose of atoms which made it a molecule, it can also be call a compound.

Answer:

I believe it is c. Molecule, Pure compound

Explanation:

this is because it is composed of atoms which create molecule.

Answer:

a

Explanation:

because it fits the diagonal trend that point toward the upper right

Answer:

[Ne] 3s² 3p¹

Explanation:

Answer:

0.00121 atm

Explanation:

Step 1: Given data

Step 2: Calculate the pressure exerted by the column of water in SI units

The pressure exerted by the column of liquid depends on the height of the column, the density of the liquid and the gravitational constant. We can calculate it using the following expression.

P = ρ × g × h

P = 1.00g/cm³ × 9.80665 m/s² × 12.5 m

P = 123 Pa

Step 3: Convert "P" to atm

We will use the conversion factor 101325 Pa = 1 atm.

123 Pa × (1 atm/101325 Pa) = 0.00121 atm

Answer:

Propionic acid reacts with NaOH(aq) to form sodium propionate and water.

Explanation:

.

Answer:

Explanation:

29.4 mL of nitric acid having molarity of .187M reacts with 22.7 mL of potassium hydroxide .

moles contained in nitric acid solution

= .0294 x .187 moles

= 5.5 x 10⁻³ moles

This must have been reacted with same amount of moles of base

moles of sodium hydroxide in 22.7 mL of solution = 5.5 x 10⁻³ moles

molarity of base solution = 5.5 x 10⁻³ / 22.7 x 10⁻³

= .24 M .

Answer:Robert Oppenheimer went on to become chairman of the General Advisory Committee of the Atomic Energy Commission, which, in October 1949, opposed the development of the hydrogen bomb. This shocking opposition led to accusations that Oppenheimer was a Communist supporter.

Explanation:

Answer:

H3PO4 is the formula for hydrophosphoric acid

The chemical formula of hydrophosphoric acid is H₃PO₄ which is a mineral acid of phosphorous.

Chemical  formula is a way of representing the number of atoms present in a compound or molecule.It is written with the help of symbols  of elements. It also makes use of brackets and subscripts.

Subscripts are used to denote number of atoms of each element and brackets indicate presence of group of atoms. Chemical formula does not contain words. Chemical formula in the simplest form  is called empirical formula.

It is not the same as structural formula and does not have any information regarding structure.It does not provide any information regarding structure of molecule as obtained in structural formula.

There are four types of chemical formula:

1)empirical formula

2) structural formula

3)condensed formula

4)molecular formula

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Answer:

c) 387g

Explanation:

Water;

Mass = 250g

Specific heat = 4.184

Initial Temp, T1 = 25 + 273 = 298K

Final Temp, T2 = 35 + 273 = 308K

Heat = ?

H = mc(T2 - T1)

H = 250 * 4.184 (308 - 298)

H = 10460 J

Iron;

Initial Temp, T2 = 95 + 273 = 368K (Upon converting to kelvin temperature)

Mass = ?

Final Temp, T1 = 35 + 273 = 308

Heat = 10460 (Heat lost by iron is qual to heat gained by water)

Specific heat = 0.45

H = mc(T2-T1)

M = 10460 / [0.45 (308 - 368)]

M = 10460 / 27

M = 387g

The mass of the iron has been calculated as 387.40 grams.

Specific heat can be defined as the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree celsius.

Since in the reaction there has been no heat loss, the heat released by iron has been equivalent to heat absorbed by the water in the calorimeter.

Heat = mass × specific heat of water × change in temperature

Heat absorbed = 250 grams × 4.184 J/g[tex]\rm ^\circ C[/tex] × (308 K - 298 K)

Heat absorbed = 10460 J

Heat released = mass × specific heat of water × change in temperature

Heat released = mass × 0.45 J/g.K × (308 K - 368 K)

Heat released = mass × 27

Heat released = Heat absorbed

Mass of Iron × 27 = 10460 J

Mass of iron = 387.40 grams.

The mass of the iron has been calculated as 387.40 grams.

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Answer:

[tex][Cu^{2+}]=0.041 M[/tex]

Explanation:

Hello!

In this case, since the molarity of a solution is defined in terms of the moles of the solute and the volume of solution, given that the concentration of Cu(NH₃)₄²⁺ is 0.041 M, and there is only one copper atom per Cu(NH₃)₄²⁺ ion, we can compute the concentration of Cu²⁺ as shown below:

[tex][Cu^{2+}]=0.041\frac{molCu(NH_3)_4^{2+}}{L}*\frac{1molCu^{2+}}{1molCu(NH_3)_4^{2+}} =0.041 \frac{molCu(NH_3)_4^{2+}}{L}[/tex]

[tex][Cu^{2+}]=0.041 M[/tex]

Best regards!

Answer:

Explanation:

A genus is a group that includes a number of very closely related species; a species within a genus includes populations of organisms that can potentially interbreed.

Answer:

choice A

Explanation:

it it occurs when a gas escapes from a container through a hole of diameter.

Answer:

A. It occurs when a gas passes through a tiny hole.

Explanation:

Edge2020

Have a great day y'all :)

Answer: Bromine water

Explanation:

Alkanes are saturated hydrocarbons with single bond and the alkenes as unsaturated hydrocarbons with double bonds.

Bromine water is a chemical reagent which is used to distinguish between alkane and alkene.

It is of orange color in solution form and turns to colorless in alkene.

The alkanes to show any reaction with bromine water.

Answer:

urorrr

Explanation:

hahhahahahahhaahah oki nam omy mymy mymy

Answer:

action, reaction

Explanation:

Answer:

for every action there is an equal and opposite reaction

Answer: multiple approaches yield the same result positively contributes to the development of a theory since it shows that the conclusions are sound and not based on other factors such as the environment of the experiment, the researches, etc.

Answer:

I'm not positive this is the answer but my guess  would be C: Evidence from multiple approaches might prevent a poorly developed theory from being accepted.

Solution :

In the process to isolate gold that has a 80 percent yield, a 3.00 g of Au is being isolated.

That is, the actual yield of Au is 3. 00 g

Therefore, we need to find the theoretical yield.

As we know,

[tex]$\text{percent yield}=\frac{\text{actual yield}}{\text{theoretical yield}} \times 100$[/tex]

[tex]$\text{theoretical yield}=\frac{\text{actual yield}}{\text{present yield}} \times 100$[/tex]

As actual yield = 3.00 g

    percent yield = 80 %

So, theoretical yield = [tex]$\frac{3.00}{80} \times 100$[/tex]

                                  = 3.75 g

Thus he should be able to get 3.75 g which is the theoretical yield of Au.

Answer:

N = 5.8 × 10²⁴ molecules

Explanation:

Step 1: Given and required data

Step 2: Calculate the number of molecules (N) in 9.6 moles of C₂H₄

To convert moles to molecules we need Avogadro's number: there are 6.02 × 10²³ molecules of C₂H₄ per mole of C₂H₄

N = n × NA

N = 9.6 mol × 6.02 × 10²³ molecules/mol

N = 5.8 × 10²⁴ molecules

Answer:

". It will mark the time since humans began altering Earth. Starting about 10,000 years ago, it is tentatively being called the Anthropocene."

i dont know if tht will help

100,000 years in the geologic history of Earth would be considered

as Anthropocene .

The first and most recent geological epoch in Earth's history when human life began to have a noticeable influence on the planet's climate, including ecosystems, and ecosystems, is referred to as the Anthropocene Epoch. This term refers to an undefined unit of geologic time.

It would be the first time since people started changing the planet. It must be tentatively referred to as the Anthropocene and began around 10,000 years ago.

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Answer:

3

Explanation:

Answer:

ionic radii is a half the distance between two ions

Explanation:

''

Answer:

answer is

Explanation:

Gallium because it has the properties which you have mentioned

The element of Group 13 would most likely have a physical and chemical properties of brittle, shiny, semiconductor, and is silver is gallium. The correct option is B.

Gallium is a chemical substance with the atomic number 31 and indeed the emblem Ga.

Gallium belongs to periodic table group 13 and is chemically similar to the other metals in the group. In standard temperature and pressure, gallium is a soft, silvery metal.

It finds widespread application in Blu-ray technology, mobile phones, blue and green LEDs, and pressure sensors for touch switches. Gallium readily alloys with the majority of metals.

It is especially useful in low-melting alloys. Because of its high boiling point, it is ideal for recording temperatures that would vaporize a thermometer.

Gallium is a rare element on Earth, but its abundance is comparable to that of lithium and lead, with a content of 19 ppm in the continental crust.

Thus, the correct option is B.

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