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Vinil7 [7]
3 years ago
13

Claim The student hopes the samples are gold, which has a density of 19.3 g/cm3 . A local geologist suggested that samples might

be pyrite, which is a mineral with a density of 5.01 g/cm3 . What is the identity of the unknown sample
Chemistry
1 answer:
spin [16.1K]3 years ago
8 0

Answer:

Pyrite.

Explanation:

In this case, for the given samples, we compute the densities considering that the volume of each sample is computed by the difference between the volume of the water + sample and the volume of water:

\rho_1=\frac{50.25g}{(60.3-50.1)mL}=4.92g/mL\\ \\\rho_2=\frac{63.56g}{(62.5-49.8)mL}=5.01g/mL\\\\\rho_3=\frac{g}{(61.5-50.2)mL}=5.10g/mL\\\\\rho_4=\frac{55.35g}{(56.7-45.6)mL}=4.99g/mL\\\\\rho_5=\frac{74.92g}{(65.3-50.3)mL}=4.99g/mL\\\\\rho_6=\frac{67.78g}{(60.8-47.5)mL}=5.10g/mL

Therefore, since the density of the samples are closer to the density of pyrite (5.01 g/cm³) we conclude that the samples are more like to be pyrite.

Best regards.

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max2010maxim [7]
<span>The pH is given by the Henderson - Hasselbalch equation:
              pH = pKa + log([A-]/[HA])
              pH = -log(</span><span>1.3 x 10^-5) + log(0.50/0.40)
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The answer to this question is 4.98.
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3 0
4 years ago
28 ml of 0.10 m hcl is added to 60 ml of 0.10 m sr(oh)2. determine the concentration of oh− in the resulting solution.
Blababa [14]
Here is an acid-base reaction. Hydrochloric acid (HCl) reacts with strontium hydroxide [ Sr(OH)2 ]

Ions H+ and OH- neutralize each other. If the amounts are not equal, one of them will be in excess. 
Follow the steps as

1. Find moles of ions: mole= Molarity * Volume (in liter) ; n= M * V OR millimole = Molarity * Volume (in ml) ;
2. Write the equation
3. Find out excess ion
4. Use final volume (V acid + V base ) to calculate concentration of excess ion.

n HCI = 28 ml * 0.10 M = 0.28 mmol, releases 0.28 mmol H+ ions
n Sr(OH)2= 60 ml * 0.10 M= 0.60 mmol, releases 2* 0.60=1.20 mmol OH- ions
since Sr(OH)2⇒ Sr2+ + 2OH-

Neutralization reaction is OH- + H+ ---> H2O. The ratio is 1:1. That means 1 mmol hydroxide ions will neutralize 1 mmol hydrogen ions. Since OH- ions are greater in amount, they will be in excess

n(OH-) - n(H+)= 1.20 - 0.28 = 0.92 mmol OH- ions UNREACTED.

Total volume= V acid + V base= 28 ml + 60 ml = 98 ml

Molarity of OH- ions= mole / Vtotal = 0.92/98= 0.009 M

The answer is 0.009 M.


5 0
3 years ago
Read 2 more answers
one reaction that produces hydrogen gas can be represented by the unbalanced chemical equation Mg(s)+HCI(aq) -&gt; MgCI(aq)+H2(g
Sonbull [250]
<h3>Answer:</h3>

128 g HCl

<h3>General Formulas and Concepts:</h3>

<u>Math</u>

<u>Pre-Algebra</u>

Order of Operations: BPEMDAS

  1. Brackets
  2. Parenthesis
  3. Exponents
  4. Multiplication
  5. Division
  6. Addition
  7. Subtraction
  • Left to Right<u> </u>

<u>Chemistry</u>

<u>Atomic Structure</u>

  • Reading a Periodic Table

<u>Stoichiometry</u>

  • Reaction Mole Ratios
  • Using Dimensional Analysis
<h3>Explanation:</h3>

<u>Step 1: Define</u>

[RxN - Unbalanced] Mg (s) + HCl (aq) → MgCl (aq) + H₂ (g)

↓

[RxN - Balanced] 2Mg (s) + 2HCl (aq) → 2MgCl (aq) + H₂ (g)

[Given] 3.25 mol Mg

[Solve] x g HCl

<u>Step 2: Identify Conversions</u>

[RxN] 2 mol Mg → 2 mol HCl

[PT] Molar Mass of H - 1.01 g/mol

[PT] Molar Mass of Cl - 35.45 g/mol

Molar Mass of HCl - 1.01 + 35.45 = 36.46 g/mol

<u>Step 3: Stoich</u>

  1. [S - DA] Set up:                                                                                                 \displaystyle 3.25 \ mol \ Mg(\frac{2 \ mol \ HCl}{2 \ mol \ Mg})(\frac{36.46 \ g \ HCl}{1 \ mol \ HCl})
  2. [S - DA] Multiply/Divide [Cancel out units]:                                                    \displaystyle 127.61 \ g \ HCl

<u>Step 4: Check</u>

<em>Follow sig fig rules and round. We are given 3 sig figs.</em>

127.61 g HCl ≈ 128 g HCl

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1. Calculate the energy of a photon with a frequency of 3x1015 Hz.<br> ?????
Afina-wow [57]

Answer:

1.99 x 10⁻¹⁸J

Explanation:

Given parameters:

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Unknown:

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Solution:

To solve this problem, we use the expression below;

     E  = hf

Where E is the energy, h is the Planck's constant and f is the frequency

Now insert the parameters and solve for E;

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