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PolarNik [594]
3 years ago
6

A librarian is interested in the numbers of books that visitors check out from the library. She examines the checkout records of

250
randomly selected adult visitors.
Identify the population and sample for this situation.

A The population is all visitors of the library; the sample is the adult visitors
of the library.
B The population is all adult visitors of the library; the sample is the 250
visitors selected.
C The population is all visitors who check out at least 1 book from the
Library; the sample is the 250 visitors selected.
D The population is the 250 visitors selected; the sample is the 250 visitors
who check out at least 1 book from the library.​
Chemistry
2 answers:
kirill115 [55]3 years ago
8 0

Answer:

The Answer is B.)The population is all adult visitors of the library; the sample is the 250 visitors selected.

Explanation:

The population is the entire group of people or things to be studied. The sample is part of the population.

miss Akunina [59]3 years ago
6 0

Answer:

The answer B

Explanation:

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Answer:

0.00230 = <u>3 significant figures</u>

Explanation:

Significant digits or figures of a given number are the digits or figures that have meaning and contributes to the precision of the given number.        

Therefore, <u>0.00230 = 3 significant figures.</u>

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Balance the following equation: H20 --&gt; H2 + O2​
MakcuM [25]

2H2O = 2H2 + O2.

<h3><u>Explanation</u>:</h3>

Balancing equations is very essential because of the fact that it represents the stoichiometric quantities of the reactants needed to react to form the product. The ratio of the weights of reactant and product are also very well understood from this.

Here in this equation, the water is broken into hydrogen and oxygen. The balanced reaction is

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Two moles of water is broken down into 2 moles of hydrogen and one mole of oxygen.

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3 years ago
Car manufacturers are developing engines that use H₂ as fuel. In Iceland, Sweden, and other parts of Scandinavia, where hydroele
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If the coulombs are supplied at 1.44 V, then 4.766 × 10¹¹ joules are produced.

(a) The reaction is

2H₂O + 2e⁻ → H₂ + 2OH⁻

According to the reaction, 2 moles of electrons flow per mole of reaction,

(b) Given

T = 25°C

Change Celsius into Kelvin

T = 25°C

   = (25 + 273 ) K

   = 298 K

<h3>What is Ideal Gas Law ?</h3>

It is expressed as

PV = nRT

Hence ,

n = \frac{PV}{RT}

   = \frac{(12)(3.5.10^{6} )}{(0.082057)(298)}

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Now, From the given reaction we can say that ,1 mole of H₂  is produced by 2 moles of electron

Hence, 1.7176 × 10⁶ mole of H₂ is produced by

= 2 × 1.7176 × 10⁶ moles of  electron

= 3.435 ×10⁶ moles of electron

We know that

charge = moles of electron × F

          =  (3.435 ×10⁶ × 96500) C

           =  3.31 × 10¹¹ C

(c) We know that,

Voltage = \frac{energy}{charge}  =  \frac{J}{C}

1.44 V = \frac{energy}{3.31 . 10^{11} }

Energy = 1.44 V × 3.31 × 10¹¹ C

            =  4.766 × 10¹¹ Joules

Thus from the above conclusion we can say that, coulombs are supplied at 1.44 V, then 4.766 × 10¹¹ joules are produced.

Learn more about Fuel Cell here : brainly.com/question/16612142

#SPJ4

Disclaimer : The question given was incomplete on portal, Here is the complete question.

Question : Car manufacturers are developing engines that use H₂ as fuel. In Iceland, Sweden, and other parts of Scandinavia countries, where hydroelectric plants produce inexpensive electric power, the H₂ can be made industrially by the electrolysis of water.

a) How many moles of electrons flow per mole of reaction ?

b) How many coulombs are needed to produce 3.53X10⁶ L of H₂ gas at   12.0 atm and 25°C.

c) If the coulombs are supplied at 1.44 V, how many joules are produced?

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