7th grade science lol help​

Answer:

Calcium flouride?

Explanation:

Quite self explanatory

Answer:

HCO₂

Explanation:

From the information given:

The mass of the elements are:

Carbon C = 26.7 g;     Hydrogen H = 2.24 g     Oxygen O = 71.1 g

To determine the empirical formula;

First thing is to find the numbers of moles of each atom.

For Carbon:

[tex]=26.7 \ g\times \dfrac{1 \ mol }{12.01 \ g} \\ \\ =2.22 \ mol \ of \ Carbon[/tex]

For Hydrogen:

[tex]=2.24 \ g\times \dfrac{1 \ mol }{1.008 \ g} \\ \\ =2.22 \ mol \ of \ Hydrogen[/tex]

For Oxygen:

[tex]=71.1 \ g\times \dfrac{1 \ mol }{1.008 \ g} \\ \\ =4.44 \ mol \ of \ oxygen[/tex]

Now; we use the smallest no of moles to divide the respective moles from above.

For carbon:

[tex]\dfrac{2.22 \ mol \ of \ carbon}{2.22} =1 \ mol \ of \ carbon[/tex]

For Hydrogen:

[tex]\dfrac{2.22 \ mol \ of \ carbon}{2.22} =1 \ mol \ of \ hydrogen[/tex]

For Oxygen:

[tex]\dfrac{4.44 \ mol \ of \ Oxygen}{2.22} =2 \ mol \ of \ oxygen[/tex]

Thus, the empirical formula is HCO₂

The correct answer is solution B!

Answer:

B.) 14

Explanation:

27-13=14 neutrons

Answer:

Fires --> These consume fuel and convert chemical energy stored in that fuel into thermal light and sound energy.

Decay -->The breakdown of dead plants and animals releases thermal energy.

Earth --> Thermal energy comes from deep inside and it is called geothermal energy.

Answer:

0 587 mL

Explanation:

First we convert 180 grams of HCl into moles, using its molar mass:

Now we can use the number of moles and the given concentration to calculate the required volume, applying the definition of molarity:

Finally we convert liters into milliliters:

The closest answer is option C, 587 mL.

The volume needed to make an 8.40 M solution of HCl is 0.587 ml.

The correct option is C.

HCl is a strong acid. It is present in our stomach to help in digesting food.

Step1: covert 180 grams into moles

Molar mass of HCl is 36.46 g

[tex]\dfrac{180 g}{36.46 g/mol } = 4.94\; mol\; HCl[/tex]

Step2: calculate the molarity

[tex]\rm Molality = \dfrac{mol}{L}\\\\\rm L = \dfrac{4.94 mol }{8.40 M} = 0.588 L\\[/tex]

Covert the liters into ml

[tex]\dfrac{0.588 L}{1000} = 588 mL[/tex]

Thus, the volume of the solution is 588 ml., nearest is option C, 587 ml.

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Answer:

14

Explanation:

Step 1: Calculate the moles corresponding to 25 g of Ba(OH)₂

The molar mass of Ba(OH)₂ is 171.34 g/mol.

25 g × 1 mol/171.34 g = 0.15 mol

Step 2: Calculate the molar concentration of Ba(OH)₂

Molarity is equal to the moles of solute divided by the liters of solution.

[Ba(OH)₂] = 0.15 mol/0.250 L = 0.60 M

Step 3: Calculate the molar concentration of OH⁻

Ba(OH)₂ is a strong base according to the following equation.

Ba(OH)₂ ⇒ Ba²⁺ + 2 OH⁻

The molar ratio of Ba(OH)₂ to OH⁻ is 1:2. The molar concentration of OH⁻ is 2/1 × 0.60 M = 1.2 M.

Step 4: Calculate the concentration of H⁺

We will use the ionic product of water expression.

Kw = 1.0 × 10⁻¹⁴ = [H⁺] × [OH⁻]

[H⁺] = 1.0 × 10⁻¹⁴/[OH⁻] = 1.0 × 10⁻¹⁴/1.2 = 8.3 × 10⁻¹⁵ M

Step 5: Calculate the pH of the solution

We will use the definition of pH.

pH = -log [H⁺] = -log 8.3 × 10⁻¹⁵ = 14

Answer:

The Lewis structure for the sulfate ion consists of a central sulfur atom with four single bonds to oxygen atoms. This yields the expected total of 32 electrons. Since the sulfur atom started with six valence electrons, two of the S-O bonds are coordinate covalent.

Explanation:

Then that means it has both.

Answer:

[tex]\boxed {\boxed {\sf \frac {1}{3} \ mol \ Al_2O_3 \approx 0.34 \ mol \ Al_2O_3}}[/tex]

Explanation:

We will use stoichiometry to solve this problem. The reaction given has a formula of

[tex]4Al+3O_2 \rightarrow 2Al_2O_3[/tex]

The coefficients tell us the number of moles necessary for the reaction.

The reaction requires 3 moles of oxygen to produce 2 moles of aluminum oxide. We can make a ratio.

[tex]\frac {3 \ mol \ O_2}{ 2\ mol \ Al_2O_3}}[/tex]

Since we are doing the reaction with 0.5 moles of oxygen, we multiply the ratio by that number.

[tex]0.5 \ mol \ O_2 *\frac {3 \ mol \ O_2}{ 2 \ mol \ Al_2O_3}}[/tex]

Flip the ratio so the moles of oxygen cancel each other out.

[tex]0.5 \ mol \ O_2 *\frac {2 \ mol \ Al_2O_3}{ 3 \ mol \ O_2}}[/tex]

[tex]0.5 *\frac {2 \ mol \ Al_2O_3}{ 3 }[/tex]

[tex]\frac {1 \ mol \ Al_2O_3}{ 3 }[/tex]

[tex]\frac {1}{3} \ mol \ Al_2O_3 = 0.33333 \ mol \ Al_2O_3 \approx 0.34 \ mol \ Al_2O_3[/tex]

0.5 moles of oxygen produces 1/3 or approximately 0.34 moles of aluminum oxide.

Answer:

a. The condition that a reaction takes place without outside help Spontaneity

b. Difference of the enthalpy (of a system) minus the product of the entropy and absolute temperature Gibbs free energy

c. Sum of the internal energy plus the product of the pressure and volume for a reaction   Enthalpy.

d. The extent of randomness in a system Entropy

e. Solution in which no more solute can be dissolved in the solven Saturated solution

Explanation:

 (a) SPONTANEITY - The quality of being natural rather than planned in advance is described as spontaneity.

(b) GIBBS FREE ENERGY - Gibbs free energy, also known as the Gibbs function, Gibbs energy, or free enthalpy, is a quantity used to quantify the maximum amount of work that can be performed in a thermodynamic system when the temperature and pressure are held constant. The symbol ‘G' stands for Gibbs free energy.

(c) ENTHALPY - The heat absorbed or released during a process at constant pressure is equal to the Enthalpy shift. While “enthalpy” is often referred to as “heat content,” most people prefer to refer to it as “enthalpy.”

(d) ENTROPY - Entropy is the amount of thermal energy in a device per unit temperature that can't be used to do useful work. Since work is produced by ordered molecular motion, entropy is also a measure of a system's molecular disorder, or randomness. For several everyday phenomena, the idea of entropy offers profound insight into the direction of spontaneous change.

(e) SATURATED SOLUTION - A saturated solution is a chemical solution that contains the maximum amount of dissolved solute in the solvent. In a saturated solution, the extra solute will not dissolve. A number of factors influence the amount of solute that can be dissolved in a solvent to form a saturated solution.                              

Answer:

about 5 hours

Explanation:

When doing this problem you mmust mulitiply 4 x 74 and divide the answer by 60 because 60=1 hour.

Answer:

The number of protons in one atom of an element determines the atom's identity, and the number of electrons determines its electrical charge. The atomic number tells you the number of protons in one atom of an element. It also tells you the number of electrons in a neutral atom of that element.

Explanation:

Answer:

false

Explanation:

All the members of one species in a particular area are referred to as a population. All the different populations that live together in an area make up a community. The community of organisms that live in a particular area, along with their nonliving surroundings, make up an ecosystem.

Answer: 1. Highest osmotic pressure : 1 M [tex]MgCl_2[/tex]

2. Lowest osmotic pressure:  1 M [tex]C_{12}H_{22}O_{11}[/tex]

Explanation:

[tex]\pi=i\times C\times R\times T[/tex]

[tex]\pi[/tex]= osmotic pressure

i = Van'T Hoff factor  

C = concentration  

T = Temperature  

1. For 1M [tex]MgCl_2[/tex]  

, i= 3 as it is a electrolyte and dissociate to give 3 ions.

[tex]MgCl_2\rightarrow Mg^{2+}+2Cl^{-}[/tex]  

2. For 1 M [tex]KCl[/tex]

, i= 2 as it is a electrolyte and dissociate to give 2 ions.

[tex]KCl\rightarrow K^{+}+Cl^{-}[/tex]

3. For  1M [tex]C_{12}H_{22}O_{11}[/tex]

, i= 1 as it is a non electrolyte and do not dissociate.  

Thus as vant hoff factor is highest for [tex]MgCl_2[/tex] thus osmotic pressure is highest for 1 M [tex]MgCl_2[/tex]

And as vant hoff factor is lowest for [tex]C_{12}H_{22}O_{11}[/tex] thus osmotic pressure is lowest for  1 M [tex]C_{12}H_{22}O_{11}[/tex]

Answer:

The limiting reactant is: H₂O

265.3 g of K₂Sn(OH)₆ are formed in the reaction.

Explanation:

The reaction is:

Sn(s) + 2KOH (aq) + 4H₂O(l)  → K₂Sn(OH)₆ (s) + 2H₂ (g)

The first step to solve is to determine the moles of each reactant:

We controlled that reaction is ballanced.

122 g . 1mol / 118.71g = 1.03 moles of Sn

134g . 1mol /56.1g = 2.39 moles of KOH

63.9 g .1mol /18g = 3.55 mol of water

Stoichiometry is 1:2:4.

Sn is the lowest reactant and water, the highest, but I can see, that water is the limiting.

1 mol of Sn needs 4 moles of H₂O to react

Then, 1.03 moles of Sn may react to (1.03 . 4)/1 = 4.12 moles.

We only have 3.55 moles. It's ok.

2 moles of KOH need 4 moles of H₂O to react

Then, 2.39 moles of KOH may react to (2.39 . 4) /2 = 4.78 moles.

We only have 3.55, there's no enough water.

So 4 moles of water can produce 1 mol of potassium hydroxystannate

Then, 3.55 moles of H₂O may produce (3.55 . 1)/4 = 0.8875 moles.

We convert moles to mass: 0.08875 mol . 298.91g /1mol =265.3g

Answer:

alpha particle needs to be added to the equation.

Explanation:

Given;

atomic mass of Americium = 241

atomic mass of neptunium = 237

The difference in atomic mass of the radioactive elements given is calculated as;

241 - 237 = 4

The particle with atomic mass of 4 is alpha particle usually represented with helium atom.

Am²⁴¹ -----> He⁴ + Np²³⁷

Thus, alpha particle needs to be added to the equation.

Answer:

4/2 HE

Explanation:

a p e x!

Answer:

Given : Diatomic molecule at 273K

'q' absorbed = positive = +100Cal = 100 x 4.184J = 418.4J

'W' done by system = negative = -209J

By first law of thermodynamics;

ΔU = q + W = 418.4 + (-209) = 209.4J

We know for diatomic molecule Cv=25R and CvΔT=ΔU

CvΔT=209.4

 25RΔT=209.4

ΔT=5R209.4×2

And, Heat exchange=Cm×ΔT 

where; Cm is molar heat capacity

Cm=ΔTHeat Exchange

substituting values for Heat Exchange = 418.4 and ΔT=5R209.4×2

Cm=5R

Answer:

Permafrost is any part of the ground that remains completely frozen or colder

Answer:

Attached picture.

Explanation:

(1) Ksp equals the product of [Co 2+][CO3 2-]. CoCO3 is excluded from the equilibrium expression because it is a pure solid. The mole ratio of Co 2+ and CO3 2- is 1:1 so their molar solubilities are the same.

(2) There is an initial concentration of 0.10 M Co 2+ so write that in the "I" row for Co 2+ on the ICE table. When you find the zeros of the quadratic when solving for "s", take the positive value rather than the negative value because concentration cannot be negative.

(3) Extra products will cause the equilibrium to consume products and form reactants. So the reverse reaction will occur faster than the forward reaction. More products mean an increased Q value compared to K, since the numerator of [tex]K = \frac{[products]}{[reactants]}[/tex] increases.

Answer:

A.

Explanation:

In an endothermic reaction heat is applied.

In an endothermic process, heat is transferred from the surroundings to the system.

What are endothermic and exothermic processes?

An exothermic process is one that gives off heat. This heat is transferred to the surroundings. An endothermic process is one in which heat has to be supplied to the system from the surroundings.

The endothermic process is a term that describes a reaction where the system absorbs the energy from its surrounding in the form of heat. A few examples of the endothermic process are photosynthesis, evaporating liquids, melting ice, etc.

The exothermic reaction is the opposite of an endothermic reaction. It releases energy by light or heat to its surrounding. A few examples are neutralization, burning of a substance, reactions of fuels, etc.

Hence, option A is the correct answer.

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Answer:

894 deg K

Explanation:

The computation is shown below:

Given that

V1 denotes the initial volume of gas = 2.00 L  

T1 denotes the initial temperature of gas = 25 + 273 = 298 K  

V2 denotes the final volume of gas  = 6.00 L  

T2 = ?

Based on the above information

Here we assume that the pressure is remain constant,

So,  

V1 ÷ T1 = V2 ÷ T2  

T2 = T1 × V2 ÷ V1

= (298)(6) ÷ (2)

= 894 deg K

Answer:

2.41x10²¹ atoms

Explanation:

mass of nickel that are present in the coin can be determined Using ( 25% nickel) with j mass of coin= 0.942g )

mass of nickel = (0.942g) × (25/100)

= 0.2355g of Nickel

We need to convert this " gram" into " moles"

Mole= mass/ molar mass

Molar mass= 58.69 g/mol

0.2355 g) / (58.69 g/mol)

= 0.004 mol

We need to convert the moles to

number of atoms.

Avogadro's number= 6.023x10²³ atoms/mol

(0.004 × 6.023x10²³ atoms/mol)

=2.41x10²¹ atoms

Answer:

4.5M

Explanation:

The solution was diluted from 2.0L to 3.0L, the dilution factor was:

3.0L / 2.0L = 1.5.

That means the solution was diluted 1.5 times.

As the final molarity of the diluted solution is 3.0M, the initial molarity of the solution was:

3.0M * 1.5 =

The statement which is  given below describe a homogeneous catalyst.

"It is in the same phase as the reactants"

The catalyst which have similar phase to the reactant of the reaction is called homogeneous catalyst.

Mostly in  homogeneous catalyst, catalyst present in liquid form.

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