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andrey2020 [161]
3 years ago
8

Gold is alloyed (mixed) with other metals to increase its hardness in making jewelry.

Chemistry
1 answer:
KiRa [710]3 years ago
4 0

Answer:

A) 54.04%

B) 13-karat

Explanation:

A) From the problem we have

<em>1)</em> Mg + Ms = 9.40 g

<em>2)</em> Vg + Vs = 0.675 cm³

Where M stands for mass, V stands for volume, and g and s stand for gold and silver respectively.

We can rewrite the first equation using the density values:

<em>3)</em> Vg * 19.3 g/cm³ + Vs * 10.5 g/cm³ = 9.40

So now we have<em> a system of two equations</em> (2 and 3) <em>with two unknowns</em>:

We <u>express Vg in terms of Vs</u>:

  • Vg + Vs = 0.675 cm³
  • Vg = 0.675 - Vs

We <u>replace the value of Vg in equation 3</u>:

  • Vg * 19.3 + Vs * 10.5 = 9.40
  • (0.675-Vs) * 19.3 + Vs * 10.5 = 9.40
  • 13.0275 - 19.3Vs + 10.5Vs = 9.40
  • -8.8 Vs + 13.0275 = 9.40
  • <u>Vs = 0.412 cm³</u>

Now we <u>calculate Vg</u>:

  • Vg + Vs = 0.675 cm³
  • Vg + 0.412 cm³ = 0.675 cm³
  • Vg = 0.263 cm³

We <u>calculate Mg from Vg</u>:

  • 0.263 cm³ * 19.3 g/cm³ = 5.08 g

We calculate the mass percentage of gold:

  • 5.08 / 9.40 * 100% = 54.04%

B)

We multiply 24 by the percentage fraction:

  • 24 * 54.04/100 = 12.97-karat ≅ 13-karat
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Pani-rosa [81]

Answer:

0.37atm

Explanation:

Given parameters:

Initial pressure  = 0.25atm

Initial temperature  = 0°C  = 273K

Final temperature  = 125°C  = 125 + 273  = 398K

Unknown:

Final pressure  = ?

Solution:

To solve this problem, we use a derivative of the combined gas law;

           \frac{P1}{T1}  = \frac{P2}{T2}

  P and T are pressure and temperature

  1 and 2 are initial and final values

        \frac{0.25}{273}   = \frac{P2}{398}  

         P2  = 0.37atm

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2 years ago
What mass of aluminum is produced by the decomposition of 5.0 kg al2o3?
Nina [5.8K]
The  mass for  of aluminum that is produced  by  the decomposition  of  5.0 Kg Al2O3 is 2647 g or 2.647  Kg

          calculation
  Write  the equation for decomposition  of Al2O3

Al2O3 = 2Al  + 3 O2

find the  moles  of  Al2O3 =  mass/molar mass

convert  5 Kg  to g   = 5 x1000 = 5000 grams
molar mass of  Al2O3 =  27 x2 + 16 x3  = 102 g/mol

 moles =5000 g/  102 g/mol = 49.0196 moles

by use  of mole ratio between Al2O3 to  Al  which is 1:2  the moles of Al = 49.0196 x2 =98.0392  moles


mass of  Al = moles x molar  mass

= 98.0392 moles x  27g/mol = 2647  grams  or 2647/1000 = 2.647 Kg


7 0
4 years ago
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Answer:  a)  _{74}^{186}\textrm{W}

b) _{80}^{201}\textrm{Hg}

c)  _{34}^{76}\textrm{Se}

d) _{94}^{239}\textrm{Pu}

Explanation:

General representation of an element is given as:_Z^A\textrm{X}

where,

Z represents Atomic number

A represents Mass number

X represents the symbol of an element

Mass number is defined as the sum of number of protons and neutrons that are present in an atom.

Mass number = Number of protons + Number of neutrons

In an atom, when neutrons or protons are lost or gains, it directly affects the mass number of an atom.

Atomic number is defined as the number of protons or number of electrons that are present in an atom.

It is characteristic of a particular element.

Atomic number = Number of electrons = Number of proton

a) Z 74, A 186: _{74}^{186}\textrm{W}

b) Z 80, A 201: _{80}^{201}\textrm{Hg}

c) Z 34, A 76: _{34}^{76}\textrm{Se}

d) Z 94, A 239.: _{94}^{239}\textrm{Pu}

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3 years ago
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ozzi

Answer:

They went from atoms to oxygen molecule.

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I'm not sure if this is the answer your teacher is looking for, but in simple terms you had 2 oxygen atoms. Together they make an oxygen molecule, which is the stuff we breathe.

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Klio2033 [76]
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