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Marizza181 [45]
4 years ago
10

An atom with an atomic number of 12 and a mass number of 25 can best be described by which of these

Chemistry
2 answers:
meriva4 years ago
8 0

A. An atom that contains 12 protons


Maslowich4 years ago
7 0

A. An atom that contains 12 protons <u><em>and 13 neutrons.</em></u>

<u><em /></u>

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What is the answer pllleeaasseeeee?????
kenny6666 [7]

I will try my best to sovle this question...

Im Pretty sure it has to be A. it needs to balance it would not stand in place if not balanced.

3 0
3 years ago
A sample contains 16 mg of polonium-218. After 12 minutes, the sample will contain 1.0 mg of polonium-218. What is the half life
mariarad [96]

Answer:

Half-life = 3 minutes

Explanation:

Using the radioactive decay equation we can solve for reaction constant, k. And by using:

K = ln2 / Half-life

We can find half-life of polonium-218

Radioactive decay:

Ln[A] = -kt + ln [A]₀

Where:

[A] could be taken as mass of polonium after t time: 1.0mg

k is Reaction constant, our incognite

t are 12 min

[A]₀ initial amount of polonium-218: 16mg

Ln[A] = -kt + ln [A]₀

Ln[1.0mg] = -k*12min + ln [16mg]

-2.7726 = - k*12min

k = 0.231min⁻¹

Half-life = ln 2 / 0.231min⁻¹

<h3>Half-life = 3 minutes</h3>

5 0
3 years ago
Which Two of the following are pure substances*
Snowcat [4.5K]

Answer:

I think A and B

Explanation:

5 0
3 years ago
Read 2 more answers
Suppose you have just added 100 ml of a solution containing 0.5 mol of acetic acid per liter to 400 ml of 0.5 m naoh. what is th
Tpy6a [65]

pH = 13.5

Explanation:

Sodium hydroxide completely ionizes in water to produce sodium ions and hydroxide ions. Hydroxide ions are in excess and neutralize all acetic acid added by the following ionic equation:

\text{HAc} + \text{OH}^{-} \to \text{Ac}^{-} + \text{H}_2\text{O}

The mixture would contain

  • 0.4 \times 0.5 - 0.1 \times 0.5 = 0.15 \; \text{mol} of \text{OH}^{-} and
  • 0.1 \times 0.5 = 0.05 \; \text{mol} of \text{Ac}^{-}

if \text{Ac}^{-} undergoes no hydrolysis; the solution is of volume 0.1 + 0.4 = 0.5 \; \text{L} after the mixing. The two species would thus be of concentration 0.30 \; \text{mol} \cdot \text{L}^{-1} and 0.10 \; \text{mol} \cdot \text{L}^{-1}, respectively.

Construct a RICE table for the hydrolysis of \text{Ac}^{-} under a basic aqueous environment (with a negligible hydronium concentration.)

\begin{array}{cccccccc} \text{R} & \text{Ac}^{-}(aq) &+ & \text{H}_2\text{O}(aq) & \leftrightharpoons & \text{HAc}(aq) & + & \text{OH}^{-} (aq)\\ \text{I} & 0.10 \; \text{M} & & & & & &0.30 \; \text{M}\\ \text{C} & -x \; \text{M}& & & & +x \; \text{M}& & +x \; \text{M} \\ \text{E} & (0.10 - x) \; \text{M} & & & & x \; \text{M} & & (0.30 +x) \; \text{M} \end{array}

The question supplied the <em>acid</em> dissociation constant pK_afor acetic acid \text{HAc}; however, calculating the hydrolysis equilibrium taking place in this basic mixture requires the <em>base</em> dissociation constant pK_b for its conjugate base, \text{Ac}^{-}. The following relationship relates the two quantities:

pK_{b} (\text{Ac}^{-}) = pK_{w} - pK_{a}( \text{HAc})

... where the water self-ionization constant pK_w \approx 14 under standard conditions. Thus pK_{b} (\text{Ac}^{-}) = 14 - 4.7 = 9.3. By the definition of pK_b:

[\text{HAc} (aq)] \cdot [\text{OH}^{-} (aq)] / [\text{Ac}^{-} (aq) ] = K_b =  10^{-pK_{b}}

x \cdot (0.3 + x) / (0.1 - x) = 10^{-9.3}

x = 1.67 \times 10^{-10} \; \text{M} \approx 0 \; \text{M}

[\text{OH}^{-}] = 0.30 +x \approx 0.30 \; \text{M}

pH = pK_{w} - pOH = 14 + \text{log}_{10}[\text{OH}^{-}] = 14 + \text{log}_{10}{0.30} = 13.5

6 0
3 years ago
1. What is the molarity of a solution prepared by dissolving 3.11 grams of NaOH in
Elena L [17]

The molarity of a solution prepared by dissolving 3.11 grams of NaOH in

enough water to make 300 milliliters of solution is 0. 256 mol/ L

Explanation:

<h3>What is Molarity?</h3>

Molarity (M) is the amount of a substance in a given volume of solution. It is otherwise known as the number of moles of solute in a certain amount of solution.

The unit of molarity is mol/L

<h3>Formula for calculating molarity :</h3>

Molarity = number of moles of solute divided by the volume of the solution\

<h3>Parameters </h3>

Molarity = ?

Number of  moles is calculated using :

Mass of the solute = 3.11 grams of NaOH

Molar mass of the solute = Na + O + H

Let's input the atomic numbers of the elements: Na (23) , O (16) , H (1)

Molar mass of NaOH = 23 + 16 + 1 = 40 g/ mol

Number of moles = 3.11 ÷ 40 = 0.077 mol

Volume of the solution is measured in Liters

Let's convert 300 milliters to liters = 300 divided by 1000 = 0.3 Liters

Molarity = 0.077 ÷ 0.3 = 0. 256 mol/ L

Therefore, the Molarity of the solution is 0. 256 mol/ L

Read more on molarity here :

brainly.com/question/26873446

3 0
2 years ago
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