If 25% of a radioactive element remains after 1,000 years, what is the half-life?

Answers

Answer 1

Answer:

Half life of the given radioactive substance after 1000 years is 500 years.

What is half life?

Half -life of a substance is defined as the time which is required for half of the quantity of a radioactive substance to get decayed.It is a term which is used in nuclear chemistry for describing how quickly unstable atoms undergo radioactive decay into other nuclear species by emitting particles or the time which is required for number of disintegrations per second of radioactive material to decrease by one half of its initial value.

For the given problem, T=1000 years and N=25% of N°

where T=time period , N=amount of quantity after decay ,N°= initial quantity.

Here,N=25% of N°

N=25/100 N°=N°/4

N°/4=N°/2 $^n$

n=2

∵nt $_1/2$ =T

So. 2t $_1/2$ =1000

t $_1/2$ =500 years.

Hence, the half-life of a substance is 500 years.

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Answer 2

Answer: The half-life would be 500 years.

25% means that 2 half-lives have already passed. So one half-life is 500 years.

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How many moles of ethyl alcohol, C2H6O, are in a 18.0 g sample?

Answers

To find moles in this sample, you would divide grams by molar mass of ethyl alcohol
(18.0g)/(46.07g/mol) = 0.391mol C2H6O

How does a warm front form

Answers

A warm front occurs when a cold air mass retreats and is replaced by a warm air mass

How can you tell when a solution is formed?

Answers

You may tell when a solution os formed when the item or particle, such as sugar or salt,
dissolves completely in the solvent, such as water.

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Under which conditions of temperature and pressure would helium behave most like an ideal gas?(1) 50 K and 20 kPa (3) 750 K and 20 kPa
(2) 50 K and 600 kPa (4) 750 K and 600 kPa

Answers

Answer : The correct option is, (3) 750 K and 20 kPa

Explanation :

The conditions for ideal gas are :

Ideal gas are those gas that has no intermolecular attractions.

Ideal gas are those gas that have negligible volume.

The ideal gas equation is,

$PV=nRT$

The conditions for real gas are :

Real gas are those gas that have intermolecular attractions.

Real gas are those gas that have volume.

The real gas equation is,

$(P+(an^2)/(V^2))(V-nb)=nRT$

A real gas behave ideally at high temperature and low pressure condition.

From the given options, option (3) have high temperature and low pressure is the correct option.

Hence, at 750 K and 20 kPa conditions of temperature and pressure does a sample of helium behave most like an ideal gas.

A compound is broken down by chemical means during (1) chromatography
(2) distillation
(3) electrolysis
(4) filtration

Answers

Answer : Option 3) Electrolysis.

Explanation : In the process of electrolysis, decomposition of the chemical is done by passing the electric current from the liquid or the solution containing ions in it. This is the process where compound is broken into ions namely, cations and anions.

Rest all options does not involves chemical decomposition of the compound.

Chromatography is a technique where rates of solute and solvent are compared in a medium where the solute components move at different rates and the separation is obtained.

Distillation simply purifies the liquid or solution by heating or cooling process.

Filtration just involves removal of impurities by using a more porous material device to get purified compound.

Answer:

The correct answer is option (3).

Explanation:

Electrolysis is defined as chemical process in which decomposition is carried out by passing an electricity in a solution containing ions. For example: electrical decomposition of water gives oxygen gas and hydrogen gas.

$2H_2O(l)\overset{Electricity}\rightarrow 2H_2(g)+O_2(g)$

where as chromatography, distillation and filtration are the separation techniques used to separate the compounds from the mixtures.

Hence, the correct answer is option (3).

What is the charge on an electron?

Answers

Answer

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Explanation:

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