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dexar [7]
3 years ago
10

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

Chemistry
1 answer:
KIM [24]3 years ago
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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Chemistry help please! I just need to make sure the answers correct.... Thank you!
Veronika [31]
1. At constant tempaerature and pressure, 3 tablets produce 600cm^3 of gas
Thus calculating for 1 tablet that produces 600 / 3 = 200 cm^3
So now two tablets produce 200 x 2 = 400 cm^3
2. We have the equation PV = nRT, n being the number of moles
Pressure P = 1,000 kPa
Volume V = 3 L
R = 8.31 L kPa/mol-K
Temperature T = 298 K
n = PV / RT = (1000 x 3) / (8.31 x 298) = 3000 / 2476.38 = 1.21 moles
Number of moles = 1.21 moles.
8 0
3 years ago
A fog over a lake. what two changes of state must occur to produce the fog? do the water molecules absorb or release energy duri
Zolol [24]
The water from the lake must first evaporate from the liquid state to the gaseous state and then condense in the air to form vapors.
The water molecules absorb energy while evaporating and release it when condensing. Their motion gets faster when they are evaporating and slows back down upon condensation.
3 0
3 years ago
Read 2 more answers
a square boat made from iron has overall dimensions of 2.00 cm x 11.0 cm x 11.0 cm. it has a mass of 213 g. water has a density
Stolb23 [73]
Density of boat  =  \frac{MASS}{VOLUME}
                           
                          =  \frac{213 g}{(2 cm  *  11 cm  *  11cm)}
 
                          =   0.88 g / cm³

Since the density of water is greater than the density of the boat ( 1 > 0.88) then that means, the boat will NOT sink.

B.

4 0
3 years ago
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Which of the following expressions is the correct equilibrium-constant expression for the equilibrium between dinitrogen tetroxi
nekit [7.7K]

Answer:

D. [NO₂]²/[N₂O₄]

Explanation:

The equilibrium constant expression for a reaction is products over reactants. Since NO₂ has a coefficient of 2, it will become an exponent.

So, it would be:

[NO₂]²/[N₂O₄]

Hope that helps.

3 0
3 years ago
Consider the following data:
VikaD [51]

∆H ° rxn =-2855.56 kJ

<h3>Further explanation</h3>

Given

ΔHf CO₂ = -393.5 kJ/mol

ΔHf H₂O = -241.82 kJ/mol

ΔHf  C₂H₆ = - 84.68 kJ/mol

Reaction

2C2H6(g) + 7O2(g) -> 4CO2(g) + 6H2O(g)

Required

ΔHrxn=

Solution

<em>∆H ° rxn = ∑n ∆Hf ° (product) - ∑n ∆Hf ° (reactants) </em>

∆H ° rxn = (4.-393.5+6.-241.82)-(2.-84.68)

∆H ° rxn = (-1574-1450.92)-(-169.36)

∆H ° rxn =-3024.92+169.36

∆H ° rxn =-2855.56 kJ

8 0
3 years ago
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