The density of the sample is:
Density = mass / volume
Density = 9.85 / 0.675
Density = 14.6 g/cm³
If the sample has 95% gold, and 5% silver, its density should be:
0.95 x 19.3 + 0.05 x 10.5
Theoretical density = 18.9 g/cm³
The difference in theoretical and actual densities is very large, making it likely that the jeweler was not telling the truth.
Answer:
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Explanation:
<u>1. Chemical balanced equation (given)</u>

<u>2. Mole ratio</u>

This is, 1 mol of NaOH will reacts with 1 mol of KHP.
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<u>3. Find the number of moles in 72.14 mL of the base</u>



<u>4. Find the number of grams of KHP that reacted</u>
The number of moles of KHP that reacted is equal to the number of moles of NaOH, 0.007055 mol
Convert moles to grams:
- mass = number moles × molar mass = 0.007055mol × 204.23g/mol
You have to round to 3 significant figures: 1.44 g (because the molarity is given with 3 significant figures).
<u>5. Find the percentage of KHP in the sample</u>
The percentage is how much of the substance is in 100 parts of the sample.
The formula is:
- % = (mass of substance / mass of sample) × 100
- % = (1.4408g/ 1.864g) × 100 = 77.3%
Answer:
I remember doing this in 7th,
1. D
2. B or D, more leaning on B though
3. A
Answer:
Ka = 1.52 E-5
Explanation:
- CH3-(CH2)2-COOH ↔ CH3(CH2)2COO- + H3O+
⇒ Ka = [H3O+][CH3)CH2)2COO-] / [CH3(CH2)2COOH]
mass balance:
⇒<em> C</em> CH3(CH2)2COOH = [CH3(CH2)2COO-] + [CH3(CH2)2COOH] = 1.0 M
charge balance:
⇒ [H3O+] = [CH3(CH2)2COO-]
⇒ Ka = [H3O+]²/(1 - [H3O+])
∴ pH = 2.41 = - Log [H3O+]
⇒ [H3O+] = 3.89 E-3 M
⇒ Ka = (3.89 E-3)² / ( 1 - 3.89 E-3 )
⇒ Ka = 1.519 E-5