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KIM [24]
2 years ago
15

You have 500,000 atoms of a radioactive substance. After 2 half-lives have past, how many atoms remain?

Chemistry
2 answers:
Aleonysh [2.5K]2 years ago
3 0

Answer:

125000

Explanation:

Because it is halved and halved again.

solong [7]2 years ago
3 0
Half life - when half of the radioactive substance has become stable

500,000/2 = 250,000 remaining after the first half life

250,000/2 = 125,000 remaining after the second


Or alternatively 1/4 x 500,000 = 125,000
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4.How element gold is different from oxygen?
V125BC [204]

Answer:

Gold is a metal, more specifically a transition metal, whereas Oxygen is a nonmetal, more specifically a reactive nonmetal. Using this information, you can compare and contrast metals, nonmetals, and metalloids.

Metals are:

Shiny

High melting point

Mostly silver or gray in color

Mostly solids at room temperature – Mercury (Hg) is a liquid at room temperature

Malleable – able to be hammered into a thin sheet

Ductile – able to be drawn/pulled into a wire

Good conductors of heat and electricity

Nonmetals are:

Dull

Low melting point

Brittle – break easily

Not malleable

Not ductile

Poor conductors of heat and electricity

Metalloids are:

Found on the “zig-zag” line on the Periodic Table of Elements

Have properties of both metals and nonmetals

Can be shiny or dull

Semiconductors – able to conduct electricity under certain conditions

Explanation:

Reccomend this site for questions llike these: https://ptable.com/#Properties

7 0
3 years ago
How to do lewis dot structure of nh3conh3
wlad13 [49]

Answer:

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Explanation:

3 0
3 years ago
A chemist dissolves 240mg of pure barium hydroxide in enough water to make up of solution. Calculate the pH of the solution. (Th
goblinko [34]

Answer:

pH = 12.22

Explanation:

<em>... To make up 170mL of solution... The temperature is 25°C...</em>

<em />

The dissolution of Barium Hydroxide, Ba(OH)₂ occurs as follows:

Ba(OH)₂ ⇄ Ba²⁺(aq) + 2OH⁻(aq)

<em>Where 1 mole of barium hydroxide produce 2 moles of hydroxide ion.</em>

<em />

To solve this question we need to convert mass of the hydroxide to moles with its molar mass. Twice these moles are moles of hydroxide ion (Based on the chemical equation). With moles of OH⁻ and the volume we can find [OH⁻] and [H⁺] using Kw. As pH = -log[H⁺], we can solve this problem:

<em>Moles Ba(OH)₂ molar mass: 171.34g/mol</em>

0.240g * (1mol / 171.34g) = 1.4x10⁻³ moles * 2 =

2.80x10⁻³ moles of OH⁻

<em>Molarity [OH⁻] and [H⁺]</em>

2.80x10⁻³ moles of OH⁻ / 0.170L = 0.01648M

As Kw at 25°C is 1x10⁻¹⁴:

Kw = 1x10⁻¹⁴ = [OH⁻] [H⁺]

[H⁺] = Kw / [OH⁻] = 1x10⁻¹⁴/0.01648M = 6.068x10⁻¹³M

<em>pH:</em>

pH = -log [H⁺]

pH = -log [6.068x10⁻¹³M]

<h3>pH = 12.22</h3>
8 0
3 years ago
Which element most likely has the same number of valence electrons as silicon(si)?
Blizzard [7]

Answer:

Carbon, germanium, tin and lead.

Explanation:

The silicon is belong to the carbon family. There are five elements in carbon family carbon, silicon, germanium, tin and lead. These five elements are present in same group i.e group fourteen. The elements present in same group have same number of valance electrons.

For example.

Carbon electronic configuration:

C₆ = [He]  2s² 2p²

Silicon electronic configuration:

Si₁₄ = [Ne] 3s² 3p²

Germanium electronic configuration:

Ge₃₂ = [Ar] 3d¹⁰ 4s² 4p²

Tin electronic configuration:

Sn₅₀ = [Kr] 4d¹⁰ 5s² 5p²

Lead electronic configuration:

Pb₈₂ = [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p²

we can see that in case of all elements there are four valance electrons, which are equal to the valance electrons of silicon.

7 0
3 years ago
Suppose 110.0 mL110.0 mL of hydrogen gas at STP combines with a stoichiometric amount of fluorine gas and the resulting hydrogen
Fittoniya [83]

Suppose 110.0 mL of hydrogen gas at STP combines with a stoichiometric amount of fluorine gas and the resulting hydrogen fluoride dissolves in water to form 150.0 mL of an aqueous solution. 0.032 M is the concentration of the resulting hydrofluoric acid.

<h3>What is Balanced Chemical Equation ?</h3>

The balanced chemical equation is the equation in which the number of atoms on the reactant side is equal to the number of atoms on the product side in an equation.

Now write the balanced chemical equation

H₂ + F₂ → 2HF

<h3>What is Ideal Gas ?</h3>

An ideal gas is a gas that obey gas laws at all temperature and pressure conditions. It have velocity and mass but do not have volume. Ideal gas is also called perfect gas. Ideal gas is a hypothetical gas.

It is expressed as:

PV = nRT

where,

P = Pressure

V = Volume

n = number of moles

R = Ideal gas constant

T = temperature

Here,

P = 1 atm   [At STP]

V = 110 ml = 0.11 L

T = 273 K   [At STP]

R = 0.0821   [Ideal gas constant]

Now put the values in above expression

PV = nRT

1 atm × 0.11 L = n × 0.0821 L.atm/ K. mol × 273 K

n = \frac{1\ \text{atm} \times 0.11\ L}{0.0821\ \text{L. atm/ K. mol} \times 273\ K}

n = 0.0049 mol

<h3>How to find the concentration of resulting solution ? </h3>

To calculate the concentration of resulting solution use the expression

C = \frac{n}{V}

   = \frac{0.0049}{0.15}  

   = 0.032 M

Thus from the above conclusion we can say that Suppose 110.0 mL of hydrogen gas at STP combines with a stoichiometric amount of fluorine gas and the resulting hydrogen fluoride dissolves in water to form 150.0 mL of an aqueous solution. 0.032 M is the concentration of the resulting hydrofluoric acid.

Learn more about the Ideal Gas here: brainly.com/question/25290815
#SPJ4

4 0
2 years ago
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