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2 years ago

Va rog ! urgent! E pt chimie

Chemistry

1 answer:

n200080 [17]2 years ago

5 0

Answer:

An element

It stays shiny

Explanation:

Pure Gold is an element.

An element is a distinct substance that cannot be split-up into simpler substances. Such substances consists of only one kind of atom.

There are over a hundred elements known to date.

As an element, Gold is classified as a metal due to its very unique set of properties.

One of the indicator that gold does not react with oxygen is that it stays shiny. It does not give rusty look when exposed to air.

Substances that combines with oxygen have a rusty look or change appearance when expose to air. For example, iron.

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The energy associated with a current is called____________

tatyana61 [14]

Answer:

D. Electrical energy

Explanation:

I assume you are talking about an electrical current.

(These are by what I know and are simplified, not an exact definition)

A. Mechanical energy is energy that something has because of motion.

B. Magnetism is the attracting and repulsing forces between magnets.

C. Geothermal energy is heat inside of the Earth. Used as source of power.

D. Electrical energy is the result of an electric charge.

8 0

2 years ago

9. The times of first sprinkler activation (in seconds) for a series of tests of fire-prevention sprinkler systems that use aque

Nezavi [6.7K]

This question is incomplete, the complete question is;

The times of first sprinkler activation (in seconds) for a series of tests of fire-prevention sprinkler systems that use aqueous film-forming foam is as follows; 27 41 22 27 23 35 30 33 24 27 28 22 24

( see " use of AFFF in sprinkler systems," Fire technology, 1975: 5)

The system has been designed so that the true average activation time is supposed to be at most 25 seconds.

Does the data indicate the design specifications have not been met?

Test the relevant hypothesis at significance level 0.05 using the P-value approach

Answer:

since p-value (0.042299) is lesser than the level of significance ( 0.05)

We Reject Null Hypothesis

Hence, There is no sufficient evidence that the true average activation time is at most 25 seconds

Explanation:

Given the data in the question;

lets consider Null and Alternative hypothesis;

Null hypothesis H₀ : There is sufficient evidence that the true average activation time is at most 25 seconds

Alternative hypothesis H₁ : There is no sufficient evidence that the true average activation time is at most 25 seconds

i.e

Null hypothesis H₀ : μ ≤ 25

Alternative hypothesis H₁ : μ > 25

level of significance σ = 0.05

first we determine the sample mean;

$x^{bar}$ = $\frac{1}{n}$ ∑ $x_{i}$

where n is sample size and ∑ $x_{i}$ is summation of all the sample;

= $\frac{1}{13}$ ( 27 + 41 + 22 + 27 + 23 + 35 + 30 + 33 + 24 + 27 + 28 + 22 + 24 )

= $\frac{1}{13}$ ( 363

sample mean $x^{bar}$ = 27.9231

next we find the standard deviation

s = √( $\frac{1}{n-1}$ ∑( $x_{i}-x^{bar}$ )²

x ( $x_{i}-x^{bar}$ ) ( $x_{i}-x^{bar}$ )²

27 -0.9231 0.8521

41 13.0769 171.0053

22 -5.9231 35.0831

27 -0.9231 0.8521

23 -4.9231 24.2369

35 7.0769 50.0825

30 2.0769 4.3135

33 5.0769 25.7749

24 -3.9231 15.3907

27 -0.9231 0.8521

28 0.0769 0.0059

22 -5.9231 35.0831

24 -3.9231 15.3907

sum 378.9229

so ∑( $x_{i}-x^{bar}$ )² = 378.9229

∴

s = √( $\frac{1}{13-1}$ ×378.9229 )

s = √31.5769

standard deviation s = 5.6193

now, the Test statistics

t = ( $x^{bar}$ - μ ) / $\frac{s}{\sqrt{n} }$

we substitute

t = ( 27.9231 - 25 ) / $\frac{5.6193}{\sqrt{13} }$

t = 2.9231 / 1.5585

t = 1.88

now degree of freedom df = n - 1 = 13 - 1 = 12

next we calculate p-value

p-value = 0.042299 ( using Execl's ( = TDIST(1.88,12,1)))

Here x=1.88, df=12, one tail

now we compare the p-value with the level of significance

since p-value (0.042299) is lesser than the level of significance ( 0.05)

We Reject Null Hypothesis

Hence, There is no sufficient evidence that the true average activation time is at most 25 seconds

3 0

3 years ago

Which element from this portion of the table chemically reacts in a way similar to the way the element chlorine (Cl) reacts? (1)

mina [271]

D. I or Iodine

This is because they are both in the same periodic family (the halogens) and thus the number of valence electrons are the same

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3 years ago

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What types of elements are shown in the polyatomic ions in model 1?

boyakko [2]

These ions are disjoint by the charge on the ion into four dissimilar tables and listed alphabetically within each table. Each polyatomic ion, has it called, chemical, formula, two dimensional drawing, and three dimensional representation are given.
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3 years ago

Is The atoms of the elements have different masses but the same volume true?

stepladder [879]

Yes, the atoms of the elements do have different masses but the same volume

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3 years ago

Va rog ! urgent! E pt chimie ​

Va rog ! urgent! E pt chimie