28.The chemical formula of a compound indicates
the source of the elements in the compound.
b. how elements are joined in the compound.
the alchemy symbols for the elements in the compound.
d. the relative proportions of the elements in the compound.

Answer: 16.21

Explanation:

A student measures the length of two pieces of paper as 8.21 in and 8.0 in. the total length is 16.21 with 4 significant figures.

The significant figures or digits are the form of scientific methd which represent the digit from zero to nine and use when the value is uncertain where starting zeros are not significant and decimal is also not a significant figure.

In the given value the total is 16.21 with 4 significant figures with it has 4 significant digits and the decimal with it is not significant after adding from which the respective value is here.

Therefore,  with 4 significant figures where the student measures the length of two pieces of paper as 8.21 in and 8.0 in. the total length is 16.21.

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Answer:

0.44L

Explanation:

Given parameters:

  Initial volume  = 0.75L

  Initial temperature  = 25°C  = 273 + 25 = 298K

  Final temperature  = -100°C  = 273 + (-100) = 173K

Unknown:

New volume of the balloon = ?

Solution:

According to Charles's law;

   "the volume of a fixed mass of a gas varies directly as its absolute temperature if the pressure is constant".

Mathematically;

    [tex]\frac{V_{1} }{T_{1} }[/tex]   =  [tex]\frac{V_{2} }{T_{2} }[/tex]  

  V and T are temperature values

  1 and 2 are the initial and final states

Insert the parameters and solve;

   [tex]\frac{0.75}{298}[/tex]   = [tex]\frac{V_{2} }{173}[/tex]  

    298V₂   = 129.75

           V₂  = 0.44L

Answer:

false

Explanation:

"When a metal reacts with hydrogen carbon dioxide gas is produced" statement is false.

A chemical reaction is a representation of symbols of the elements to indicate the amount of substance and moles of reactant and product.

Generally, metals do not react with hydrogen. But some metals like sodium, potassium, calcium and magnesium force the hydrogen atom to accept the electrons given by these elements and form salt-like ionic solid compounds called metal hydrides.

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Answer:

46.32 mL

Explanation:

We'll begin by writing the balanced equation for the reaction. This is illustrated below:

2HNO₃ + Ca(OH)₂ —> Ca(NO₃)₂ + 2H₂O

From the balanced equation above,

The following data were obtained:

Mole ratio of the acid, HNO₃ (nA) = 2

Mole ratio of the base, Ca(OH)₂ (nB) = 1

Next, we shall write out the data obtained from the question. This includes:

Molarity of the acid, HNO₃ (Ma) = 0.181 M

Volume of the base, Ca(OH)₂ (Vb) = 25.1 mL

Molarity of the base, Ca(OH)₂ (Mb) = 0.167 M

Volume of the acid, HNO₃ (Va) =?

Finally, we shall determine the volume of the acid, HNO₃ as shown below:

MaVa/ MbVb = nA/nB

0.181 × Va / 0.167 × 25.1 = 2/1

0.181 × Va / 4.1917 = 2

Cross multiply

0.181 × Va = 4.1917 × 2

0.181 × Va = 8.3834

Divide both side by 0.181

Va = 8.3834 / 0.181

Va = 46.32 mL

Therefore, the nitric acid, HNO₃ required for the reaction is 46.32 mL

Answer:

The answer is B

Explanation:

I had the same question and I chose B and it was correct.

Answer:

B. Carbon needs more than just three bonds to reach a noble gas

Explanation:

PLATO ANSWER

PLATO EXPLANATION-

Each hydrogen atom can make only one bond, but a carbon atom needs four bonds to be stable. Therefore, three hydrogen atoms are not enough for the carbon atom to make four bonds.

C : 52.2%, H : 13.1%, O:34.7%

The empirical formula is the smallest comparison of atoms of compound forming elements.  

A molecular formula is a formula that shows the number of atomic elements that make up a compound.  

(empirical formula) n = molecular formula  

11.5 g of Ethanol-C₂H₅OH contains 6.00 g of Carbon and 1.51 g of Hydrogen.

mass of Oxygen :

[tex]\tt 11.5-(6+1.51)=4~g[/tex]

Percent composition :

[tex]\tt \dfrac{6}{11.5}\times 100\%=52.2\%[/tex]

[tex]\tt \dfrac{1.51}{11.5}\times 100\%=13.1\%[/tex]

[tex]\tt \dfrac{4}{11.5}\times 100\5=34.7\%[/tex]

Answer:

Explanation:

no of molecules=5.65*10^21

NA=6.23*10^23

no of moles=no of molecules/avogadro number

no of moles=5.65*10^21/6.23*10^23

no of moles=9.07*10^-3

now we know that

no of moles=mass/molar mass

mass=no of moles*molar mass

mass=9.07*10^-3*89.06

mass=0.808 g

Answer:

Universe.

Explanation:

Biosphere is just a planet. Solar system contains planets and star. Galaxy holds multiple solar systems only. Universe hold everything, biospheres, solar systems, and galaxies. I hope this helps :D

Answer:

B.

Explanation:

A solar system is IN a galaxy. Its not A.

A Galaxy doesnt have other galaxies in it. Its not c

A biosphere is only referring to earth. its not D.

Therefore, it is B. A universe is everything in outer space including stars, planets, and galaxies.

Answer:

85,020 milligrams

Explanation:

Multiply the mass value by 1,000

Answer:

1.5 × 10² mL

Explanation:

Step 1: Given data

Step 2: Calculate the final volume of the gas

For an ideal gas, we can calculate the final volume of the gas using Boyle's law.

P₁ × V₁ = P₂ × V₂

V₂ = P₁ × V₁/P₂

V₂ = 1.9 atm × 80 mL/1.0 atm

V₂ = 1.5 × 10² mL

Since the pressure decreased, the volume of the gas increased.

The concentrations : 0.15 M

pH=11.21

The ionization of ammonia in water :

NH₃+H₂O⇒NH₄OH

NH₃+H₂O⇒NH₄⁺ + OH⁻

The concentrations of all species present in the solution = 0.15 M

Kb=1.8 x 10⁻⁵

M=0.15

[tex]\tt [OH^-]=\sqrt{Kb.M}\\\\(OH^-]=\sqrt{1.8\times 10^{-5}\times 0.15}\\\\(OH^-]=\sqrt{2.7\times 10^{-6}}=1.64\times 10^{-3}[/tex]

[tex]\tt pOH=-log[OH^-]\\\\pOH=3-log~1.64=2.79\\\\pH=14-2.79=11.21[/tex]

Alcohol is both a Depressant and a Muscle Relaxer. Therefore the answer would be both!

Hope this helps :)

Answer:

-114kJ mol-1

Explanation:

Definition of the enthalpy change of neutralization: the energy released with the formation of 1 mole of water when neutralization takes place between an acid and a base.

Since both reactions yield the same number of moles of water, the answer should be -114kJ mol-1.

The statement for the enthalpy change of reaction 2 is "-114 kJ"

The change in enthalpy (ΔH) is a quantity of heat of a system. The enthalpy change is the amount of heat that enters or exits a system during a reaction.

One equivalent of hydrogen ions is neutralised with one equivalent of hydroxide ions in the reaction 1,

NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

The change in enthalpy is given as -114 kJ.

Two equivalents of hydrogen ions are neutralised with two equivalents of hydroxide ions in the reaction 2,

Ba(OH)2 + H2SO4 (aq) → BaSO4 (s) + 2H2O (l)

But, that primary ionic reaction is same for both the reaction in which hydrogen ion combines with hydroxide ion to generate a water molecule. So, the enthalpy change of reaction 1 would be exactly same as for reaction 2.

The neutralization enthalpy comes out to be -114 kJ.

Hence the correct answer is -114 kJ.

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Answer:

93.5 kPa

Explanation:

Step 1: Given data

Step 2: Convert the temperatures to the Kelvin scale

When working with gases, we need to consider the absolute temperature. We will convert from Celsius to Kelvin using the following expression.

K = °C + 273.15

T₁: K = 50°C + 273.15 = 323 K

T₂: K = 100°C + 275.15 = 373 K

Step 3: Calculate the final pressure of the gas

At a constant volume, we can calculate the final pressure of the gas using Gay-Lussac's law.

P₁/T₁ = P₂/T₂

P₂ = P₁ × T₂/T₁

P₂ = 81.0 kPa × 373 K/323 K

P₂ = 93.5 kPa

Answer:

M = 17 M

Explanation:

Given data:

Mass of sodium hydroxide = 678.57 g

Volume of solution = 1.00 L

Molarity  of solution = ?

Solution:

Molarity is used to describe the concentration of solution. It tells how many moles are dissolve in per litter of solution.

Formula:

Molarity = number of moles of solute / L of solution

Number of moles of sodium hydroxide:

Number of moles = mass/molar mass

Number of moles = 678.57 g /40 g/mol

Number of moles = 17 mol

Molarity:

M =  17 mol/1.00 L

M = 17 mol/L

M = 17 M

Answer:

Watch Naruto that's the answer

Explanation:

Answer:

Fair test.

PLS GIVE BRAINLIEST

We are given:

Mass of NaCl in the given solution = 22.3 grams

Volume of the given solution = 2 L

Number of Moles of NaCl:

We know that the number of moles = Given mass / Molar mass

Number of moles = 22.3 / 58.44 = 0.382 moles

Molarity of NaCl in the Given solution:

We know that Molarity of a solution = Moles of Solute / Volume of Solution(in L)

Molarity = 0.382 / 2

Molarity = 0.191 M

Graphite is sometimes used to reduce the friction between two surfaces that are rubbing together. Therefore, this happen because of weak covalent bond.

Graphite is among the most prevalent carbon allotropes. It is also the stable allotrope for carbon, and as such, it is employed in electrochemistry to define the heat of synthesis of carbon compounds. With a hardness of 2.09-2.23 g/cm3, graphite is an excellent conductor of electricity and heat.

Graphite is a large covalent structure in which each carbon atom is covalently linked to three other carbon atoms. Graphite is sometimes used to reduce the friction between two surfaces that are rubbing together. This happen because of weak covalent bond.

Therefore, graphite is sometimes used to reduce the friction between two surfaces that are rubbing together. This happen because of weak covalent bond.

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Answer:

[tex]T_f=26.7\°C[/tex]

Explanation:

Hello.

In this case, when two substances at different temperature are placed in contact in an isolated container, we can say that the heat lost by the hot substance is gained by the cold substance. In such a way, since granite is at 76.0 °C and water at 22.0 °C we infer granite is hot and water is cold, so we write:

[tex]Q_{granite}=-Q_{water}[/tex]

In terms of mass, specific heat and change in temperature, we write:

[tex]m_{granite}C_{granite}(T_f-T_{granite})=-m_{water}C_{water}(T_f-T_{water})[/tex]

Thus, since the temperature is the same for both substance, we can solve for it as shown below:

[tex]T_f=\frac{m_{granite}C_{granite}T_{granite}+m_{water}C_{water}T_{water}}{m_{granite}C_{granite}+m_{water}C_{water}}[/tex]

By plugging in each variable, we obtain:

[tex]T_f=\frac{11.1g*0.790\frac{J}{g\°C} *76.0\°C+22.0g*4.18\frac{J}{g\°C} *22.0\°C}{11.1g*0.790\frac{J}{g\°C} +22.0g*4.18\frac{J}{g\°C}}\\\\T_f=26.7\°C[/tex]

Best regards!

Answer:

A. 2 Fe, 3 S and 12 O

B. 43 moles of H

C. 1.0×10² moles of C

Explanation:

A. Formula for iron (III) sulfate is Fe₂(SO₄)₃

This salt has 2 atoms of iron and 3 sulfates, so in total we have:

2 Fe, 3 S and 12 O

Pay attention to the subscripts

B. Formula for quinine is: C₂₀H₂₄N₂O₂

If we continue with the example before we can say that 1 mol of Iron (III) sulfate contains 2 moles of Fe, 3 moles of S and 12 moles of O

Then, 1 mol of quinine contains 24 moles of H

So 1.8 moles of quinine, may contain (1.8 . 24) /1 = 43 moles of H

C.  1 mol of quinine contains 20 moles of C

5.4 moles of quinine may contain (5.4 . 20) /1 = 1.0×10²

(As the answer must be in 2 significant figures and the real answer is 108, I had to use scientific notation)

D. People with different goals can make contributions to scientific knowledge

Both Schwann and Virchow had different thoughts and ideas. Schwann wanted to understand how cells worked - Virchow wanted to know the origin of diseases. Different goals.

Answer:

D

Explanation:

I got it right on studyisland

Hydrogen can only form single covalent bonds when forming molecular compounds. Therefore, option B is correct.

A covalent bond is a type of chemical bond formed between two or more atoms in which electrons are shared between them. Covalent bonds usually occur between nonmetal atoms and are formed by the sharing of valence electrons.

Hydrogen can only form a single covalent bond because it has only one valence electron and needs one more electron to complete its valence shell, making it stable.

Nitrogen can form triple covalent bonds, carbon can form multiple covalent bonds, and oxygen can form double covalent bonds in molecular compounds.

Thus, option B is correct.

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Answer:

Mass of CO₂ produced = 20.328 g

Oxygen is limiting reagent.

Explanation:

Given data:

Mass of C₂H₂ = 13.7 g

Mass of O₂ = 18.5 g

Mass of CO₂ produced = ?

What is limiting reagent = ?

Solution:

Chemical equation:

2C₂H₂ + 5O₂      →     4CO₂ + 2H₂O

Number of moles of C₂H₂:

Number of moles = mass /molar mass

Number of moles = 13.7 g/ 26.04 g/mol

Number of moles = 0.526 mol

Number of moles of O₂:

Number of moles = mass /molar mass

Number of moles = 18.5 g/ 32 g/mol

Number of moles = 0.578 mol

Now we will compare the moles of CO₂ with C₂H₂ and O₂

                      C₂H₂              :                CO₂

                           2                :                 4

                       0.526            :              4/2×0.526 = 1.052

                      O₂                  :                   CO₂

                        5                   :                     4

                      0.578             :                4/5×0.578 = 0.462

The number of moles of  CO₂ produced by O₂  are less thus oxygen will be limiting reactant.

Mass of CO₂ produced:

Mass = number of moles × molar mass

Mass = 0.462 mol × 44 g/mol

Mass = 20.328 g

Moles of MgF₂ : 1.2 x 10⁻⁴

Maybe the complete question is like this

A student prepares 100. mL of a saturated solution of MgF2 by adding 0.50 g of solid MgF2 to 100. mL  of distilled water at 25°C and stirring until no more solid dissolves. (Assume that the volume of the  undissolved MgF2 is negligibly small.) The saturated solution is analyzed, and it is determined that [F−] in  the solution is 2.4 × 10−3 M.

The dissociation reaction of MgF₂

MgF₂(s)⇒ Mg²⁺(aq)+2F⁻(aq)

mol ratio MgF₂ : F⁻ = 1 : 2

mol of F⁻ in 100 ml solution :

[tex]\tt mol=M\times V\\\\mol=2.4\times 10^{-3}\times 0.1=2.4\times 10^{-4}[/tex]

mol MgF₂ :

[tex]\tt \dfrac{1}{2}\times 2.4\times 10^{-4}= 1.2\times 10^{-4}[/tex]

Answer:

Physical Change. Physical changes are changes in which no bonds are broken or formed. This means that the same types of compounds or elements that were there at the beginning of the change are there at the end of the change.

The work energy of this process : 2337.298 J

The laws of thermodynamics 1 state that: energy can be changed but cannot be destroyed or created  

ΔU=Q-W

Q=m.c.Δt

[tex]\tt Q=8.85\times 2.650\times 63.2=1482.198~J[/tex]

the work (W) :

[tex]\tt W=Q-\Delta U\\\\W=1482.198-(-855.1)=2337.298~J[/tex]

Answer:

4moles of carbon trihydride