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The question is incomplete, the complete question is;

We obviously cannot wait for 4 million years to determine the half-life of technetium, or even 87.7 years to determine the half-life of plutonium. The half-life of a substance is determined using a Geiger counter, which is essentially a tube filled with an inert gas. When a particle decays and produces radiation, it briefly ionizes the gas and produces a detectable electric pulse, which is amplified and counted by a detector (before digital displays were available, you would hear clicks and see a needle register on a dial). Determine the formula for the half-life of a substance with an initial count of No pulses and a count of N1 pulses M minutes later.

Answer:

M1/2 = 0.693/k

Explanation:

Given that the initial count rate is No pulses

The count rate after M minutes is N1

Then from;

A = Aoe^-kt

A= N1

Ao=No

I can now write;

N1 = Noe^-kM

The half life is the time taken for the activity of the radioactive nuclide to reach half its initial value. Hence;

N1/No =e^-kM = 1/2

Taking natural logarithm of both sides as shown below;

-kM1/2 = ln(1/2)

M1/2 = -  (ln(1/2)/k)

M1/2 = 0.693/k

Answer:

A. When two aqueous solutions are mixed, a precipitate is formed.

Explanation:

The precipitate (a solid substance that falls from the liquid) is the result of a chemical reaction taking place between the liquids.

The other three answer choices are indicative of physical changes (temperature change, phase change, color change).

When two aqueous solutions are mixed, a precipitate is formed indicates that a chemical change has occurred.  

Hence, option A is correct answer.

Chemical change are those changes in which substance changes chemical composition. These changes are permanent changes. In chemical change new substances formed and in chemical change substances can not get back into its original form. It is irreversible change.

Physical changes are those changes in which substance changes physical properties only. Properties like temperature, pressure, shape, color, size, state (solid, liquid and gas). These changes are temporary in nature. In physical change no new substances formed. It is reversible change.

Now, check all the options one by one:

Option (A): When two aqueous solutions are mixed, a precipitate is formed is a chemical change. Since precipitation indicate a chemical reaction (that is double displacement reaction).

Option (B): As ammonium nitrate dissolved in water causes the temperature to decrease is a physical change because heat energy is absorbed here and it is a endothermic reaction.

Option (C): Alcohol evaporates when left in an open container is a physical change because evaporation is a physical change as it changes the state from liquid state to gas state.

Option (D): Water is added to blue copper (II) chloride solution. The resulting mixture if lighter blue in color is a physical change as properties like change in color is physical change.  

Thus, from above conclusion we can say that When two aqueous solutions are mixed, a precipitate is formed indicates that a chemical change has occurred.  

Hence, option A is correct answer.

Learn more about physical and chemical change here: https://brainly.com/question/17166994

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Answer:

Answer is B

Explanation:

It's not A because we're boiling only water.

It's not C because the last dot for 2 cups ends at 70 min while the last dot for 4 cups ends at 90 min.

It's not D because water boils at around 100 C, as shown in the graph. The highest dot for both 2 cups and 4 cups were about the same near 100 C.

The graph shows that 4 cups of water is able to retain heat more (higher heat capacity), so it takes more time for water to cool down than 2 cups of water.

Answer:

0.800 mol of O2

Explanation:

Calculate the moles of oxygen produced by the reaction of 0.800mol of carbon dioxide.

The balanced equation for the reaction is given as;

6CO2 + 6H2O → C6H12O6 + 6O2  

From the reaction;

6 mol of CO2 produces 6 mol of O2

0.0800 mol of CO2 would produce x mol of O2

6 = 6

0.0800 = x

Solving for x;

x = 6 * 0.800 / 6

x = 0.800 mol

Answer:

B and D

Explanation:

Because its adaptions they need to survive in the cold.

Answer:

2 no. is the answer surface currents that move in a path opposite to the wind currents

Answer:

no.2 is the answer of your question

Answer:

There are two dots are present on the left side of calcium atom which represents the unpaired electrons present in the outermost shell. This structure is presented by Lewis in order to show the number of unpaired electrons in the atom.

Explanation:

Answer:

Grade A is the best percentage that is developing, proficient, exceeding, and emerging

Answer:

D. A pond freezing over is not a chemical reaction, it is a physical reaction.

Answer:

Explanation:

A graduated cylinder was filled to 30.0 mL with a liquid. An unknown metal cylinder having a mass of 60.27 g was submerged in the in the liquid. The final volume of the liquid level was 45.2 mL.

a. Calculate the density of the unknown metal cylinder.

b. The density of the liquid is 0.899 g/mL. What is the mass of the liquid in the graduated cylinder?

Answer:

4.375 moles Na2CO3

Explanation:

Formula for molarity is;

M = n/V

Where;

M is molarity

n is number of moles

V is volume

Making n the subject we have;

n = VM

We are given;

M = 1.75 M

V = 2.5 L

Thus;

n = 2.5 × 1.75

n = 4.375 moles Na2CO3

Answer:

4.375 moles Na2CO3

Explanation:

Have a great day

Answer:

Mass

Explanation:

Answer

% of C in C2H6= (2×12)/30×100=80%

% of H in C2H6= (3×2)/30×100=20%

Explanation:

2C+3H2-C2H6

nC=12, nH=1, nC2H6=30

2moles of C-1mole of C2H6

3moles of H-1 mole of C2H6

% of C in C2H6= (2×12)/30×100=80%

% of H in C2H6= (3×2)/30×100=20%

Answer:

1- veins

2-aorta

3-valve

4-ventricles

5-atrium

Answer:

the percentage composition of mass of nitrogen in NH OH is 42.86 %

Answer:

your finger becomes negatively charged

Explanation:

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Answer:

The amount of energy available at level A depend on energy provided from an a biotic source

Answer:

A

Explanation:

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Answer:

Elecric charge/ Electricity  

Explanation:

Electric charge is the net gain or loss of electrons

I hope im right!!

Answer: arterioles

Explanation:

Answer:

2 N

Explanation:

Answer:

513.975g

Explanation:

I'm assuming that the question has Aluminium and Chlorine as the question is not clear.

1. Balance the equation

  2 Al + 3 Cl2  → 2AlCl3

2. Use the mole = mass/mr equation and molar ratio to find the mass of AlCl3

   133.5 x 3.85 = 513.975g

Answer:

Mechanical

Explanation:

Answer: true

Explanation:

Thermal efficiency of process heating equipment

Answer:

True

Explanation:

Answer: The coefficients are 2, 2 and 1.

Explanation: According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants.

The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

The balanced chemical equation for the given reaction is:

2H2o➡️2h2+o2

Answer:

letting the car fall down the ramp i got that right.

Explanation:

Answer:

77.81 g of CuNO₃

Explanation:

6 CuNO₃  +  Al₂(SO₄)₃  ⇒  3 Cu₂SO₄  +  2 Al(NO₃)₃

This is your chemical equation.  We will need this information for converting from Al(NO₃)₃ to CuNO₃.

First, convert grams of Al(NO₃)₃ into moles using the molar mass.

[tex]44.0g*\frac{mol}{213.01g} = 0.2065mol[/tex]

Next, convert moles of Al(NO₃)₃ to moles of CuNO₃.  You can do this by using the stoichiometry (the numbers in front of the compounds).  For every 6 moles of CuNO₃, you will get 2 moles of Al(NO₃)₃, causing the ratio of CuNO₃ to Al(NO₃)₃ to be 6:2.

[tex]0.2065mol*\frac{6}{2} =0.6197mol[/tex]

Now that you moles of CuNO₃, convert this to grams using its molar mass.

[tex]0.6197 mol * \frac{125.56g}{mol} =77.81 g[/tex]

You will need 77.81 grams of CuNO₃ to produce 44.0 grams of Al(NO₃)₃.