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Sophie [7]
3 years ago
10

How do researchers select a sample that is representative of its population

Chemistry
1 answer:
tiny-mole [99]3 years ago
7 0

Explanation:

Using stratified random sampling, researchers must identify characteristics, divide the population into strata, and proportionally choose individuals for the representative sample. ... For example, individuals who are too busy to participate will be under-represented in the representative sample.

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If calcium chloride is dissolved in water, what can be said about the concentration of the calcium ion? a. It has the same conce
e-lub [12.9K]

Answer:

b. Its concentration is half that of the chloride ion

Explanation:

As the calcium chloride formula is CaCl2

CaCl2 <--> Ca + 2 Cl-

4 0
3 years ago
On the pH scale pure water has a pH of<br> A. 0<br> B. 7<br> C. 14
konstantin123 [22]

Answer:its b 7

Explanation:

7 is neutral and pure water is the middle man

7 0
3 years ago
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For this reaction: 4 Al + 3O2 = 2 Al2O3
MariettaO [177]
0.347 mols, working out shown on photo

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3 years ago
For question numbers 1 and 2, two statements are given - one labelled
Svetllana [295]

Answer:

(iv) (A) is false, but (R) is true.

Explanation:

It is not true that carbon has a strong tendency to either lose or gain electrons to attain noble gas configuration. Carbon is a member of group 14, it is the first member of the group and carbon is purely a non metal. Only metals metals can loose electrons to attain the noble gas configuration. Moreover, carbon does not participate in ionic bonding so it does not gain electrons to attain the noble gas configuration.

However, carbon participates in covalent bonding where it is covalently bonded to four other chemical species using its four outermost electrons. Carbon forms covalent bonds in which four electrons are shared with other chemical species.

5 0
3 years ago
A drop of water weighing 0.48 g is vaporized at 100 ?c and condenses on the surface of a 55-g block of aluminum that is initiall
irakobra [83]
<h3><u>Answer;</u></h3>

<em>-49 °C</em>

<h3><u>Explanation and solution;</u></h3>
  • Considering the fact that, the specific heat capacity of aluminum is 0.903 J/g x C, and the heat of vaporization of water at 25 C is 44.0 KJ/mol.  

Moles water = 0.48 g / 18.02 g/mol

                      =0.0266  moles

<em>Heat lost by water</em> = 0.0266 mol x 44.0 kJ/mol

                                 =1.17 kJ => 1170 J  

<em>But heat lost =heat gained</em>

<em>Therefore;</em> Heat gained by aluminium = 1170 J  

        1170 = 55 x 0.903 ( T - 25) = 49.7 T - 1242  

                   1170 + 1242 = 49.7 T  

            T = 48.5 °C ( 49 °C <em>at two significant figures)</em>

<em>Hence</em>, final temperature = 49 °C

4 0
3 years ago
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