All categories

3 years ago

After two half-lives, how much of the original material has decayed? 25 percent 50 percent 75 percent 100 percent

Chemistry

2 answers:

AfilCa [17]3 years ago

7 0

Answer:

75% of the material has decayed.

Explanation:

Hello,

We can start this problem by solving the first half-life assuming the arbitrary condition stating that the initial concentration has a value of 100M, thus, for the first half-life, the concentration dwindles to 50M. Afterwards, the second half-life yields a concentration of 25M, meaning that the 75% of the material has decayed up to the second half-life, of course, the half of the result from the first half-life.

Best regards.

Kryger [21]3 years ago

5 0

Answer:

After two half lives the sample will remain 25%.

Explanation:

Given data:

Number of half lives given = 2

Mass remain after two half lives = ?

Solution:

Consider that original sample is 100 g.

At time zero = 100 g

After first half life = 100 /2 = 50 g

After second half life = 50 g/ 2 = 25 g

So after two half lives the sample will remain 25%.

You might be interested in

Gaseous ethane (CH,CH,) will react with gaseous oxygen (0,) to produce gaseous carbon dioxide (CO) and gaseous water (H2O). Supp

notka56 [123]

Answer:

0.00 g

Explanation:

We have the masses of two reactants, so this is a limiting reactant problem.

We will need a balanced equation with masses, moles, and molar masses of the compounds involved.

1. Gather all the information in one place with molar masses above the formulas and masses below them.

Mᵣ 30.07 32.00

2CH₃CH₃ + 7O₂ ⟶ 4CO₂ + 6H₂O

Mass/g: 1.50 11.

2. Calculate the moles of each reactant

$\text{moles of C$_{2}$H}_{6} = \text{1.50 g C$_{2}$H}_{6} \times \dfrac{\text{1 mol C$_{2}$H}_{6}}{\text{30.07 g C$_{2}$H}_{6}} = \text{0.04988 mol C$_{2}$H}_{6}\\\\\text{moles of O}_{2} = \text{11. g O}_{2} \times \dfrac{\text{1 mol O}_{2}}{\text{32.00 g O}_{2}} = \text{0.34 mol O}_{2}$

3. Calculate the moles of CO₂ we can obtain from each reactant

From ethane:

The molar ratio is 4 mol CO₂:2 mol C₂H₆

$\text{Moles of CO}_{2} = \text{0.04988 mol C$_{2}$H}_{6} \times \dfrac{\text{4 mol CO}_{2}}{\text{2 mol C$_{2}$H}_{6}} = \text{0.09976 mol CO}_{2}$

From oxygen:

The molar ratio is 4 mol CO₂:7 mol O₂

$\text{Moles of CO}_{2} = \text{0.34 mol O}_{2}\times \dfrac{\text{4 mol CO}_{2}}{\text{7 mol O}_{2}} = \text{0.20 mol CO}_{2}$

4. Identify the limiting and excess reactants

The limiting reactant is ethane, because it gives the smaller amount of CO₂.

The excess reactant is oxygen.

5. Mass of ethane left over.

Ethane is the limiting reactant. It will be completely used up.

The mass of ethane left over will be 0.00 g.

8 0

3 years ago

A mixture of helium, nitrogen, and oxygen has a total pressure of 752 mm Hg. The

NISA [10]

Answer: The partial pressure of oxygen in the mixture is 321 mm Hg

Explanation:

According to Dalton's law, the total pressure is the sum of individual pressures.

$p_{total}=p_{He}+p_{N_2}+p_{O_2}$

Given : $p_{total}$ = total pressure of gases = 752 mm Hg

$p_{He}$ = partial pressure of Helium = 234 mm Hg

$p_{N_2}$ = partial pressure of nitrogen = 197 mm Hg

$p_{O_2}$ = partial pressure of oxygen = ?

Putting in the values we get:

$752mmHg=234mmHg+197mmHg+p_{O_2}$

$p_{O_2}=321mmHg$

The partial pressure of oxygen in the mixture is 321 mm Hg

5 0

3 years ago

If Oxygen gains 2 electrons<br> what charge will it have?

Scilla [17]

Answer:

A very powerful one

Explanation:

7 0

3 years ago

What is the correct clases for this drugs <br> Promethazine<br><br> heelp me please

Maslowich

Answer:

MedlinePlus Drugs Information

Explanation:

Promethazine is in a class of medication called phenothiazines

6 0

3 years ago

topjm [15]

Explanation:

Because they share a similar composition, similar chemicals affect their structures in positive or negative ways. For example, fluoride – a staple in many dental practices – strengthens both enamel and eggshells and helps protect them from acids. Acids weaken and break down both substances. Scientists find this particularly concerning given that the ocean is growing increasingly acidic. They fear this may weaken the eggs of some marine species and harm their chance of survival. Most dentists recommend limiting aggressively acidic foods and beverages such as soft drinks.

3 0

3 years ago

Read 2 more answers