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3 years ago

There's a 50 gram sample of our Ra-229 it is half-life is 4 minutes how much will be left after 12 minutes

1 answer:

7 0

The half life of an isotope is the amount of time it will take for the given isotope to decay till the point where it reaches half of what amount you had started with.

If the half life of Ra-229 is 4 minutes then every 4 minutes the sample is reduced to half of what you had before

4 minutes.) 50/2 Ra-229 --> 25g Ra-229

8 minutes.) 25/2 Ra-229 --> 12.5 Ra-229

12 minutes.) 12.5/2 Ra-229 --> 6.25 Ra-229 remaining

<em>I beleive this is the correct answer</em>

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In general, the value of the equilibrium constant for a chemical reaction does NOT depend on_________.

mart [117]

Answer: Option (B) is the correct answer.

Explanation:

Equilibrium constant is defined as the relationship present between the amounts of products and reactants which are there at equilibrium in a reversible chemical reaction at a given temperature.

For example, $A + B \rightleftharpoons C + D$

Mathematically, $K_{eq} = [C][D]$

As the value of equilibrium constant depends on rate constants of the forward and reverse reactions. And, this rate of reaction also changes with change in pressure and temperature.

Therefore, it will also lead to change in equilibrium constant but it does not depend on initial amount pf reactants.

Thus, we can conclude that in general, the value of the equilibrium constant for a chemical reaction does NOT depend on the initial amounts of reactants present.

4 0

3 years ago

A 0.271g sample of an unknown vapor occupies 294ml at 140C and 874mmHg. The emperical formula of the compound is CH2. How many m

Phoenix [80]

Using PV = nRT, we can calculate the moles of the sample.
874 mmHg = 116,524 Pa
n = PV/RT
n = 116,524 x 294 x 10⁻⁶ / 8.314 x (140 + 273)
n = 9.98 x 10⁻³ mol

moles = mass / Mr
Mr = 0.271/9.98 x 10⁻³
Mr = 27.2
Mass of empirical formula = 14
Repeat units = 27.2 / 14 ≈ 2

Formula of substance:
C₂H₄

Combustion equation:
C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

1 mole produces 2 moles of CO₂, so 3 moles will produce 6 moles CO₂

7 0

3 years ago

Substances have more kinetic energy in the _______ state than in the _______ state. A. Gas; solid B. Solid; gas C. Solid; liquid

Elodia [21]

Substances have more kinetic energy in the gas state than in the solid state

6 0

3 years ago

A catalyst

kotegsom [21]

A catalyst speeds up the rate of reaction so the answer is B.

8 0

3 years ago

Need help with this chem question thanks

IRISSAK [1]

Answer:

The answer to your question is letter A.

Explanation:

Isomers are molecules that have the same molecular formula but have a different structure. The molecule from which are looking an isomer has 5 carbons and 1 double bond. Then we need to look for another molecule with these components.

A.- This molecule has 5 carbons and 1 double bond, This structure is an isomer of the first one.

B.- This molecule has 3 carbons and 1 double bond, it's not an isomer of the first structure.

C. This molecule has 4 carbons and 1 triple bonds, it's not an isomer of the first structure.

D. This molecule has 5 carbons but it doesn't have any double bond, then it's not an isomer of the first structure.

5 0

3 years ago