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vlabodo [156]
3 years ago
10

How many days have passed if 4.80 mg of calcium-47 decayed to 1.2 mg of calcium-47?

Chemistry
1 answer:
LenaWriter [7]3 years ago
6 0
(1) 36 days is 8 half-life periods,
so 24mg becomes 24mg times (1/2)^8 = 24 mg/256 = 0.094 mg

(2) 9.6/1.2 = 8, which means three half-life periods went by.
At the end of 4.5 days, there were 4.8 mg
At the end of 9.0 days, there were 2.4 mg
At the end of 13.5 days, there were 1.2 mg

(3) The activity is proportional to the amount of radioactive material remaining,
so after two half-life periods, the activity should be 1/4 of what it originally was.
So the initial activity was probably 12.0 Ci
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There are 55.0 g of neon gas in a 3.0 L cylinder, the pressure is 4.5 atm what is the temp of the gas
marshall27 [118]

Answer:

60.9 Kelvin

Explanation: First, write out everything that you know. You are tring to find the temperature, so the temperature will be represented by x.

Pressure (P)= 4.5 atm

Volume (V)= 3L

Number of Moles (n)= ?

Gas Consant (R)= 0.0821, if the pressure is in atm, that means r is 0.0821

Temperature (T)= x

We don't have all the information we need to plug the values into the equation. We still need to know how many moles 55.0 grans of neon is.

Ne in Grams= 55

Atomic Mass of Ne= 20.1797

55/20.1797= 2.7  

moles= 2.7

Now that we have all the information we need, plug everying into the equation. In case you don't know, the Ideal Gas Law Equation is PV= nRT.

(4.5)(3) = (2.7)(0.821)x    

x= 60.9

Now you have your temperature! It is 60.9 in Kelvin.

4 0
3 years ago
Nitrogen dioxide reacts with water to form nitric acid and nitrogen monoxide according to the equation: 3NO2(g)+H2O(l)→2HNO3(l)+
Vera_Pavlovna [14]

Answer:

5 moles of NO₂ will remain after the reaction is complete

Explanation:

We state the reaction:

3NO₂(g) + H₂O(l) → 2HNO₃(l) + NO(g)

3 moles of nitric oxide can react with 1 mol of water. Ratio is 3:1, so we make this rule of three:

If 3 moles of nitric oxide need 1 mol of water to react

Then, 26 moles of NO₂ may need (26 .1) / 3 = 8.67 moles of H₂O

We have 7 moles of water but we need 8.67 moles, so water is the limiting reactant because we do not have enough. In conclusion, the oxide is the reagent in excess. We can verify:

1 mol of water needs 3 moles of oxide to react

Therefore, 7 moles of water  will need (7 .3)/1 = 21 moles of oxide

We have 26 moles of NO₂ and we need 21, so we still have oxide after the reaction is complete. We will have (26-21) = 5 moles of oxide that remains

5 0
2 years ago
Imagine the reaction A + B ⇌ C + D is at equilibrium, where the forward and reverse reactions are at equal rates. What would hap
kondaur [170]

Answer:

Rate of forward reaction will increase.

Explanation:

Effect of change in reaction condition on equilibrium is explained by Le Chatelier's principle. According to this principle,

If an equilibrium condition of a dynamic reversible reaction is disturbed by changing concentration, temperature, pressure, volume, etc,  then reaction will move will in a direction which counteract the change.

In the given reaction,

A + B ⇌ C + D

If concentration of A is increase, then reaction will move in a direction which decreases the concentration of A to reestablish the equilibrium.

As concentration A decreases in forward direction, therefore, rate of forward reaction will increase.

3 0
3 years ago
Which is longer DNA or chromosone
Sliva [168]

Answer:

DNA

Explanation: Because if you stretch DNA it gets longer.

8 0
3 years ago
Read 2 more answers
Question 3 (1 point)
pentagon [3]

Full question:

The IUPAC name for  CH3CH2C≡CCH3 is:

Answer:

2-pentyne

Explanation:

To name hydrocarbons, you first you have to identify the longest carbon chain.  There are 5 carbons in this chain, so we know the name is "pent".

You then have to identify the presence of any double or triple bonds. If double bonds, it is an alkene, if triple bonds, it is an alkyne. In this case there is a triple bond, so we know the hydrocarbon is pentyne.

You then number the chain to give the lowest number to the triple bond. It could either be 4 (countnig carbons from left to right) or 2 (from right to left). Therefore, the answer is 2-pentyne.

5 0
3 years ago
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