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3 years ago

Identifying Characteristics of Atoms

Chemistry

1 answer:

Anon25 [30]3 years ago

8 0

Explanation:

The number of protons in an atom is the atomic number.

Mass number is the number of protons plus neutrons in an atom.

Mass number = number of protons + number of neutrons

Atomic number = number of protons

Atomic number gives the symbol of the element

Number Number Atomic Mass Symbol

Protons neutrons Number Number

A 7 B 15 C

D E 26 56 F

A, number of protons = B

Mass number = protons + neutrons

15 = protons + 7

Protons = 15 - 7 = 8

Atomic number 8 is for oxygen = C

Atomic number = number of protons = D = 26

Number of neutrons ;

E = Neutrons = mass number - protons = 56 - 26 = 30

Atomic number 26 is for Iron = F

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Answer:

pOH = 0.36

Explanation:

Both potassium hydroxide and lithium hydroxide solutions are strong bases, so you assume 100% dissociation.

1. Potassium hydroxide solution, KOH

Volume, V = 304 mL = 0.304 liter

Molarity, M = 0.36 M

number of moles, n = M × V = 0.36M × 0.304 liter = 0.10944 mol

1 mole of KOH produces 1 mol of OH⁻ ion, thus the number of moles of OH⁻ is 0.10944

2. LIthium hydroxide, LiOH

Volume, V = 341 mL = 0.341 liter

Molarity, M = 0.51 M

number of moles, n = M × V = 0.341 liter × 0.51 M = 0.17391 mol

1mole of LiOH produces 1 mol of OH⁻ ion, thus the number of moles of OH⁻ is 0.17391

3. Resulting solution

Number of moles of OH⁻ ions = 0.10944 mol + 0.17391 mol = 0.28335 mol

Volume of solution = 0.304 liter + 0.341 liter = 0.645 liter

Molar concentration = 0.28335 mol / 0.645 liter = 0.4393 M

4. pOH

$pOH=-\log [OH^-]=-\log (0.439)=0.36$ ← answer

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SOLVE A 4.80-gram piece of magnesium displaces 2.76 mL of water when it is placed in a graduated cylinder. What is the density o

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Answer:

Density = 1.74 gm/mL

Explanation:

Given that:

Mass of piece of Magnesium = 4.80 grams

The volume displaced by this piece = 2.76mL

Let us learn about a property:

Volume of water displaced by a substance when immersed in the water is equal to the Volume of the substance itself.

So, volume of the piece of Magnesium = 2.76 mL

To find:

Density of magnesium = ?

Solution:

Let us have a look at the formula for Density of a Substance:

Density of a substance is given as the ratio of mass of substance and the volume of that mass of substance.

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$Density = \dfrac{Mass}{Volume}$

Putting the given values:

$Density = \dfrac{4.80}{2.76}\\\Rightarrow \bold{Density = 1.74\ gm/mL}$

So, the answer is:

Density of Magnesium = 1.74 gm/mL

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