Subject is actually science please answer giving brainliest also!

Answer:

The half-life varies depending on the isotope.

Half-lives range from fractions of a second to billions of years.

The half-life of a particular isotope is constant.

Explanation:

Make sure you add the options

Answer:

gill lamellae

Explanation:

Gills  in fishes are structures that permit fish to carry out gaseous exchange in water.  Fishes exchange gases  such as oxygen and carbon dioxide using gills.

Fish gills carry out their activity mainly through its major component called the  gill lamellae. These are comb-like filaments which help increase the surface area of the gills in order to facilitate gaseous exchange

Answer:

[NH3] = 0.270M

[NH4Cl] = 0.327M

Explanation:

The HNO3 will react with the weak base, NH3, as follows:

HNO₃ + NH₃ → NH₄⁺ + NO₃⁻

Initial moles of each specie of the buffer:

NH3 = NH4⁺ 0.210L * (0.300mol/L) = 0.063moles

The moles added of HNO3 = Additional moles of NH4Cl and the moles substracted of NH3:

0.001L * (6mol / L) = 0.006 moles.

After the addition:

Moles NH3 = 0.063mol - 0.006mol = 0.057moles

Moles NH4Cl = 0.063mol + 0.006mol = 0.0069moles

And their concentrations are:

[NH3] = 0.057moles / 0.211L = 0.270M

[NH4Cl] = 0.069moles / 0.211L = 0.327M

Answer:

C. three

Explanation:

Answer:

d. Pergoldic acid

Explanation:

chlorate = ClO₃⁻

Goldate GoO₃⁻

On this basis we can infer that HClO₄ and HGoO₄ will be similar .

HClO₄ is called perchloric acid , hence HGoO₄ will be called pergoldic acid.

Answer:

Final volume  = 0.44 L

Explanation:

Given data:

Initial volume of balloon = 1.1 L

Initial pressure = 0.80 atm

Final volume = ?

Final pressure = 2.0 atm

Solution:

The given problem will be solved through the Boly's law,

"The volume of given amount of gas is inversely proportional to its pressure by keeping the temperature and number of moles constant"

Mathematical expression:

P₁V₁ = P₂V₂

P₁ = Initial pressure

V₁ = initial volume

P₂ = final pressure

V₂ = final volume  

Now we will put the values in formula,

P₁V₁ = P₂V₂

0.80 atm × 1.1 L = 2.0 atm × V₂

V₂ = 0.88 atm. L/ 2.0 atm

V₂ = 0.44 L

Answer:

THE ANSWER IS D UR WELCOME.

Explanation:

Answer:

0.0132 g CuSO₄

General Formulas and Concepts:

[tex]\text{Molarity}=\frac{\text{moles of solute}}{\text{liters of solution}}[/tex]

Explanation:

Step 1: Define variables

3.29 mL

4.00 M CuSO₄

x g CuSO₄

Step 2: Define conversions

1000 mL = 1 L

Step 3: Solve

Step 4: Simplify

We are given 3 sig figs.

0.01316 g CuSO₄ ≈ 0.0132 g CuSO₄

Answer:

The wood sample has an age of approximately 22800 years.

Explanation:

The Becquerel ([tex]Bq[/tex]) is a SI unit which describes radioactive activity related to decay of radioactive isotopes, which is equivalent to [tex]\frac{1}{s}[/tex]. The decay of radioactive isotope is described by the following ordinary differential equation:

[tex]\frac{dN}{dt} = -\frac{N}{\tau}[/tex] (Eq. 1)

Where:

[tex]\frac{dN}{dt}[/tex] - Disintegration rate, measured in [tex]\frac{1}{s}[/tex].

[tex]N[/tex] - Amount of remaining radioactive nuclei, dimensionless.

[tex]\tau[/tex] - Time constant, measured in seconds.

By integration the solution of this differential equation is obtained:

[tex]\int {\frac{dN}{N} } = -\frac{t}{\tau}\int dt[/tex]

[tex]\ln N = -\frac{t}{\tau} + C[/tex]

[tex]N(t) = N_{o}\cdot e^{-\frac{t}{\tau} }[/tex] (Eq. 2)

Let [tex]N_{1}[/tex] and [tex]N_{2}[/tex] different disintegration rates for Carbon-14 samples, so that:

[tex]N_{1} = N_{o} \cdot e^{-\frac{t_{1}}{\tau} }[/tex] (Eq. 3)

[tex]N_{2} = N_{o}\cdot e^{-\frac{t_{2}}{\tau} }[/tex] (Eq. 4)

If we divide (Eq. 4) by (Eq. 3), then:

[tex]\frac{N_{2}}{N_{1}} = \frac{N_{o}\cdot e^{-\frac{t_{2}}{\tau} }}{N_{o}\cdot e^{-\frac{t_{1}}{\tau} }}[/tex]

[tex]\frac{N_{2}}{N_{1}} = e^{-\frac{1}{\tau}\cdot (t_{2}-t_{1}) }[/tex] (Eq. 5)

If [tex]\Delta t = t_{2}-t_{1}[/tex], we proceed to clear that variable:

[tex]\ln \frac{N_{2}}{N_{1}} = -\frac{1}{\tau}\cdot \Delta t[/tex]

[tex]\Delta t = -\tau\cdot \ln \frac{N_{2}}{N_{1}}[/tex] (Eq. 6)

Time constant is also a function of half-life ([tex]t_{1/2}[/tex]), measured in seconds:

[tex]\tau = \frac{t_{1/2}}{\ln 2}[/tex]

If [tex]t_{1/2} = 1.798\times 10^{11}\,s[/tex], [tex]N_{1} = 14\,\frac{1}{s}[/tex] and [tex]N_{2} = 0.875\,\frac{1}{s}[/tex],  the age of the wood sample is:

[tex]\tau = \frac{1.798\times 10^{11}\,s}{\ln 2}[/tex]

[tex]\tau = 2.594\times 10^{11}\,s[/tex]

[tex]\Delta t = -(2.594\times 10^{11}\,s)\cdot \ln \left(\frac{0.875\,\frac{1}{s} }{14\,\frac{1}{s} } \right)[/tex]

[tex]\Delta t \approx 7.192\times 10^{11}\,s[/tex]

[tex]\Delta t \approx 22805.682\,yr[/tex]

The wood sample has an age of approximately 22800 years.

Answer:

T

Explanation:

A Spider is a creepy crawly with no vertebrae and more than 6 jointed legs.

The Spider belongs to the class Arachnida . The Spider can be referred to as a non-vertebrates hence , they don't have a vertebrae(backbone).

The Spider and Cockroach are both non-vertebrates but with different pairs of legs. A cockroach is belongs to the class Insecta in which those under this class have only six jointed legs.

The Spider has eight jointed legs which is more than six and is a characteristic of Arachnids.

A snake on the other hand is a vertebrate which exempts it from being the answer.

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Ions can be made by single element or covalently bonded group of elements. The covalently bonded group of elements is called polyatomic ions or polyatomic atoms. In order to form an ion, a Group 2 element will loose two electrons and form a cation.

Any species that contain charge whether it is positive charge or negative charge is called ions. The example of polyatomic ions are sulfate, phosphate, nitrate etc.

Cation is the species that loose electron and attain positive charge while anion is a species which gain electron and attains negative charge so when anion and cation combine in fixed ration the the overall charge of the molecule is zero that is molecule is neutral, the charge over cation and anion is also called oxidation state.  In order to form an ion, a Group 2 element will loose two electrons and form a cation.

Therefore, in order to form an ion, a Group 2 element will

loose two electrons and form a cation.

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Answer:

helium

Explanation:

remaining three are efficient gas

Among the options given below, helium is not an efficient greenhouse gas. Thus, the correct option for this question is A.

Greenhouse gases are those gases that significantly allow solar radiation in order to enter but prevent the escape of heat radiations of longer wavelengths. The names of common greenhouse gases are carbon dioxide, methane, nitrous oxide, CFCs, etc.

According to the context of this question, the presence of these gases in the atmosphere is responsible for the phenomenon of keeping the earth warm. This is known as Greenhouse effect. These gases stimulate the phenomenon of global warming.

Therefore, among the options given below, helium is not an efficient greenhouse gas. Thus, the correct option for this question is A.

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Answer:

Not sure dude goodluck

Explanation:

Answer:

To get the number of atoms in this sample, we first need the number of moles of lead in 11.3 grams

Number of moles of Lead:

Molar mass of lead = 207 grams / mol

Number of moles  = given mass / molar mass

Number of moles = 11.3 / 207

Number of moles = 0.05 moles

Number of atoms of lead in 11.3 gram sample:

Number of atoms = Number of moles * avogadro's number

Number of atoms = 0.05 * 6.022 * 10²³

Number of atoms = 5 * 10⁻² * 10²³ * 6.022

Number of atoms = 30.11 * 10²¹

11.3 g block of lead contains 3.29×10²² atoms

From Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.022×10²³ atoms. Thus,

1 mole of lead = 6.022×10²³ atoms

Recall:

1 mole of lead = 207 g

Thus,

With the above information in mind, we can obtain the number of atoms in 11.3 g block of lead as illustrated below:

207 g of lead = 6.022×10²³ atoms

Therefore,

11.3 g of lead = (11.3 × 6.022×10²³) / 207

Thus, 11.3 g block of lead contains 3.29×10²² atoms

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Answer:

The effect is the increasing of the molar concentration.

Explanation:

When you standarize a solution of NaOH with KHP you are establish its molar concentration (That is the amount of moles of NaOH per liter of solution).

If you evaporated some water of the solution, you are increasing its concentration because volume is decreasing doing the amount of moles per liter increasing.

Answer: The equilibrium concentration of [tex]H_2(g)[/tex] at 700 degrees Celsius is 0.0012 M

Explanation:

Equilibrium constant is defined as the ratio of concentration of products to the concentration of reactants each raised to the power their stoichiometric ratios. It is expressed as [tex]K_c [/tex]

Moles of  [tex]H_2S[/tex] = 0.29 mole

Volume of solution = 3.0 L

Initial concentration of [tex]H_2S[/tex] = [tex]\frac{0.29mol}{3.0L}=0.097M[/tex]

The given balanced equilibrium reaction is,

                    [tex]2H_2S(g)\rightleftharpoons 2H_2(g)+S_2(g)[/tex]

         Initial conc.         0.097 M           0M          0M

At eqm. conc.    (0.097-2x) M            (2x) M   (x) M

The expression for [tex]K_c[/tex] is written as:

[tex]K_c=\frac{[H_2]^2\times [S_2]}{[H_2S]^2}[/tex]

[tex]K_c=\frac{(2x)^2\times x}{(0.097-2x)^2}[/tex]

[tex]9.30\times 10^{-8}=\frac{(2x)^2\times x}{(0.097-2x)^2}[/tex]

[tex]x=0.00060[/tex]

Equilibrium concentration of [tex][H_2][/tex]= 2x= [tex]2\times 0.00060=0.0012M[/tex]

Answer:

B

Explanation:

It's the only thing that actually changes into something different and when u burn it it makes chemicals

Answer:

What subject is this for?

Explanation:

Answer:

True

Explanation:

According to some calculations, the Earth is losing 50,000 metric tons of mass every single year, even though an extra 40,000 metric tons of space dust converge onto the Earth's gravity well, it's still losing weight.

Answer:

true

Explanation:

Answer: Proton - positive charge (+)

Neutron - neutral charge (0)

Electron - negative charge (-)

Explanation:

Answer:

See explanation

Explanation:

The compound ClO2 has 19 valence electrons.  ClO2 is a bent molecule with tetrahedral electron pair geometry but has two  lone pairs of electrons. This is indicated by the presence of four electron pairs on the outermost shell of the central atom.

The molecule has an odd number of valence electrons, hence, it is generally regarded as a paramagnetic radical. None of the proposed Lewis structures for the molecule is satisfactory because none of them obeys the octet rule.

From the images attached, one can easily see that the electron dots around the oxygen and chlorine atoms does not satisfy the octet rule in all the resonance structures shown.

The pressure can be increased by a factor of 3 by decreasing the volume by a factor of 3.

Given that the temperature of the system is held constant. So it implies that it is an isothermal process.

Now we know that the ideal gas equation is given by:

PV = nRT

where, P is the pressure

V is the volume

n is the number of moles

R is the gas constant, and

T is the temperature

Assuming n is constant, R is universal as constant, so if T is also constant, then:

PV = constant

So if P becomes 3P. that is the pressure increased by a factor of 3, then V must become V/3, so that: (3P)(V/3) = PV = constant.

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Answer:

Pour the mixture through a filter to separate the sand, then evaporate the liquid to separate the salt.

Explanation:

There are various methods used to separate single substances from a mixture. The method adopted depends upon the type of mixture and the ingredients used in it. According to the given question, the mixture comprises of sand, salt and water. Here, the first process will be the process of filtration. Through filtration, the salt-water solution and sand can be separated. Salt-water solution can be separated by the process of evaporation in which sat and water will be separated individually.

Complete Question

Sodium carbonate, Na2CO3(s), can be prepared by heating sodium bicarbonate, NaHCO3(s).

2NaHCO3(s) ------> Na2CO3(s) + CO2(g) + H2O(g) Kp = 0.23 at 100oC

If a sample of NaHCO3 is placed in an evacuated flask and allowed to achieve equilibrium at 100oC, what will the total gas pressure be?

Answer:

The value is  [tex]P_T  = 0.959 \  atm [/tex]

Explanation:

From the question we are told that

   The equation is  

[tex]2NaHCO_3_{(s)} \rightarrow  Na_2CO_3_{(s)} + CO2_{(g)} + H2O_{(g)}[/tex]

Generally the equilibrium partial pressure is mathematically represented as

    [tex]K_p =  P_{CO_2} + P_{H_2O}[/tex]

Here  

   [tex] P_{CO_2} \ and  \  P_{H_2O}[/tex] are partial  pressures of  [tex] CO_2 \ and  \ H_2O [/tex] gases

Note: when writing the formula for equilibrium partial pressure we consider only the gas in the reaction

Let assume that    

    [tex]P_{CO_2} =  a[/tex]

Generally  [tex]P_{CO_2} = P_{H_2O}[/tex] since they are both products of the reaction

  So  

       [tex]K_p =  a^2 [/tex]

From the question we are told that [tex]K_p =  0.23 [/tex]

So  

     [tex] 0.23=  a^2 [/tex]

=>  [tex] a = \sqrt{0.23} [/tex]

=>  [tex] a = \sqrt{0.23} [/tex]

=>  [tex] a = 0.4796  \ atm [/tex]

So

     [tex]P_{CO_2} =  0.4796  \ atm[/tex]

and

      [tex]P_{H_2O} =  0.4796  \ atm [/tex]

So the total pressure is

      [tex]P_T  =  0.4796  +  0.4796[/tex]

=>   [tex]P_T  = 0.959 \  atm [/tex]

Answer:

48dm³

Explanation:

Given reaction:

                  Ca(OH)₂ + 2HBr →  CaBr₂ + 2H₂O

Parameters:

Concentration of HBr = 0.5M

 Volume of Ca(OH)₂ = 40mL

 Concentration of  Ca(OH)₂ = 0.3M

Solution:

To solve this problem, we are going to use the mole concept. We solve from the known specie to the unknown.

 We first find the number of moles of the known specie which is the Ca(OH)₂ ;

                number of moles  = concentration x volume

                number of moles  = 0.3 x 40 x 10⁻³ = 0.012moles

From the reaction equation;

           1 mole of Ca(OH)₂  requires 2 moles HBr

          0.012 moles of Ca(OH)₂ will require 0.012 x 2  = 0.024moles of HBr

Now,

 To find the volume of HBr;

          Volume  = [tex]\frac{number of moles }{concentration}[/tex]

          Volume  = [tex]\frac{0.024}{0.5}[/tex]   = 0.048dm³

In mL;

       Volume 0.048 x 1000 = 48dm³

Answer:

pH = 11

Explanation:

The equilibrium of a weak base as NaCN in water is:

NaCN(aq) + H₂O(l) ⇄ OH⁻(aq) + Na⁺(aq) + HCN(aq)

And kb, the equilibrium constant, is:

Kb = [OH⁻] [HCN] / [NaCN]

Where Kb of NaCN is 2.04x10⁻⁵

In the beginning, the [NaCN] is 0.050mol / L = 0.050M.

Both [OH⁻] and [HCN] are produced from this equilibrium, and its concentration is X, that is:

2.04x10⁻⁵ = [X] [X] / [0.050M]

1.02x10⁻⁶ = X²

X = 1x10⁻³ = [OH⁻]

As pOH = - log [OH⁻]

pOH = 3.00

And pH = 14 - pOH

Answer:

The answer is actually 3. The disorder of a system.

Answer:

C. 0.35cm

Explanation:

The length indicated by the arrow along the ruler should recorded be recorded as "0.35cm".

This is correct because when counting the measurement on the ruler, the first line on the ruler is 0.1cm, the second line is 0.2cm, and so on. The spaces between each line is 0.05cm. So, the arrow is pointing on the space between 0.3cm and 0.4cm.

Therefore, 0.3cm + 0.05cm = 0.35cm.(answer).

Answer:

800

Explanation:

took the test and got it right

The numbers represent the change in energy for a chemical reaction. They are calculated by subtracting the energy of products from the energy of reactants. 800 would result from an endothermic reaction.Therefore, the correct option is D.

There are different types of reactions, such as the endothermic reaction, where the energy is used for the product's formation, and the exothermic reaction.

The energy is released in an exothermic reaction, resulting in a negative result, whereas the energy is used in an endothermic reaction, resulting in a positive result.

Any chemical reaction that absorbs heat from its surroundings is an endothermic reaction. The absorbed energy serves as the activation energy for the reaction to take place.

Thus, 800 would result from an endothermic reaction, the correct option is D.

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Your question is incomplete, most probably your question was

The numbers represent the change in energy for a chemical reaction. They are calculated by subtracting the energy of products from the energy of reactants. Which number would result from an endothermic reaction?

–212

0

-1

800