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3 years ago

How many milligrams remain of a 15.0 mg sample of radium-226 after 6396 years? The half life of radium-226 is 1599 years.

1 answer:

3 0

There are 4 half lives of radium-226 in 6396 years. 15.0 divided by half 4 times (15.0/2= 7.5, 7.5/2 = 3.75, 3.75/2 = 1.875) equals 1.875 mg of radium-226.

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An atom of which element has the greatest attraction for the electrons in a bond with a hydrogen atom?

Nadusha1986 [10]

The question can be changed into a new form:
Which element has the most negative electron affinity, or attraction for electrons? halogens have the highest electron affinities, and thus are more attracted to the electrons in the Hydrogen atom than any element in their respective periods.
In this case all the following choices are in the same period, thus Cl or Chlorine is the answer as it is a halogen.

7 0

3 years ago

A sample was prepared by mixing 18. ml of 3.00 x 10^-3 m crystal violet (cv) with 2.00 ml of 0.250 m naoh. calculate the resulti

Aleks [24]

Answer : The resulting concentrations of CV and NaOH are 0.0027 M and 0.025 M respectively.

Explanation :

Step 1 : Find moles of crystal violet and NaOH.

The molarity formula is

$Molarity = \frac{mol}{L}$

Molarity of crystal violet = $3.00 \times 10^{-3} = \frac{mol (CrystalViolet)}{L}$

The volume of crystal violet solution is 18 mL which is 0.018 L.

Moles of crystal violet = $3.00 \times 10^{-3} \times 0.018 = 5.4 \times 10^{-5}$

Moles of crystal violet = 5.4 x 10⁻⁵

Moles of NaOH = $Molarity \times L = 0.250 \times 0.00200 = 5.00 \times 10^{-4}$

Moles of NaOH = 5.00 x 10⁻⁴

Step 2 : Find total volume of the solution

The total volume of the solution after mixing NaOH and crystal violet is

0.018 L + 0.00200 = 0.020 L

Step 3 : Use molarity formula to find final concentrations

Molarity of crystal violet = $\frac{mol(CrystalViolet)}{Total Volume(L) } = \frac{5.4 \times 10^{-5}}{0.020} = 2.7 \times 10^{-3}$

Final concentration of CV = 0.0027 M

Molarity of NaOH= $\frac{mol(NaOH)}{Total Volume(L) } = \frac{5.00 \times 10^{-4}}{0.020} = 0.025 \times 10^{-3}$

NaOH is a strong base and dissociates completely as follows.

$NaOH (aq) \rightarrow Na^{+} (aq) + OH^{-} (aq)$

The mole ratio of NaOH and OH⁻ is 1:1 . Therefore the concentration of OH⁻ is same as that of NaOH.

Concentration of OH⁻ = 0.025 M

8 0

3 years ago

What does the chemical formula CaCl, show about the compound it represents? It is made up of one element. It is made up of two e

zavuch27 [327]

Answer:

It is made up of two elements.

Explanation:

To answer the question given above,

We shall determine the number of elements present in CaCl₂. This can be obtained as follow:

CaCl₂ contains calcium (Ca) and chlorine gas (Cl₂).

This implies that CaCl₂ contains two different elements.

Now, considering the options given in the question above, CaCl₂ is made up of two elements.

5 0

2 years ago

How much heat is required to vaporize 25g of water at 100*c

ElenaW [278]

Answer:

Heat required = 13,325 calories or 55.75 KJ.

Explanation:

To convert a water to steam at 100 degree celsius to vapor, we have to give latent heat of vaporization to water

Which equals ,

Q = mL,

Where, m is the mass of water present

L = specific latent heat of vaporization

Here , m= 25 gram

L equals to 533 calories (or 2230 Joules)

So, Q = 25×533 = 13,325 Calories

Or , Q = 55,750 Joules = 55.75 KJ

so, Heat required = 13,325 calories or 55.75 KJ.

4 0

3 years ago

Explain why lithium is a strong reducing agent, whereas fluorine is a strong oxidizing agent.

Tom [10]

Lithium is a good reducing agent because it is electropositive [it rapidly gains electrons]
fluorine is good oxidizing agent electronegative [it loses electrons fastly]

3 0

3 years ago