Answer:
The size of the sample needed = 67.65
Explanation:
Given that :
The margin of error = 10% = 0.10
The confidence level = 90% = 0.90
Level of significance = 1 - 0.90 = 0.10
At ∝ = 0.10
Since the proportion of people that supported him/her is not given, we assumed p = 0.50
The margin of error formula can be expressed as:
Squaring both sides; we have:
n = 67.65
Therefore, the required sample size = 67.65
C. Come to a complete stop begin the stop line
The pH where you might be able to precipitate as much Cu2 as possible will be any value that is less than 5.85.
<h3>How to illustrate the information?</h3>
The solubility product of salt is defined as the product of molar concentrations of ions in a saturated solution of it.
An ion will be precipitated if the ionic product exceeds the solubility product of the cation. In the case of Cu and Zn, the solubility product is greater for Zinc than Copper.
Also Cu will be precipitated in an acidic medium while Zn is precipitated in an alkaline medium. We have for CuS, K= S2 so S = 2.4495*10-8. For ZnS, S = 0.1414. So the lower the pH higher will be the amount of CuS precipitated.
If we are starting with 0.075M CuS and ZnS solution it will have 0.075 moles each of Cu2+, Zn2+, and S2. Since the anion concentration can be equated to POH, POH for Cus and Zns are 14.096 and 5.85.
The maximum precipitation will take place is any value which is less than 5.85.
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