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jarptica [38.1K]
3 years ago
14

What event marks the beginning of Earth's current era?

Chemistry
2 answers:
Firlakuza [10]3 years ago
4 0
It’s B a mass extinction

uysha [10]3 years ago
3 0
B. We are in the cenzoic era so what previously had happen to cause the life we live today was a huge mass extinction.... hope this helps!!
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An environmental scientist developed a new analytical method for the determination of cadmium (cd^2+) in mussels. To validate th
Anettt [7]

Answer:

The method is accurate  in the calculation of the Cu^+2

Explanation:

As a first step we have to calculate the <u>average concentration </u>of Cu^+2 find it by the method.

\frac{0.782+0.762+0.825+0.838+0.761 }{5} =0.79 ppm

Then we have to find the<u> standard deviation:</u>

s=\sqrt{\frac{1}{N-1}\sum_{i=1}^N(x_i-\bar{x})^2}=0.0359

For the confidence interval we have to use the formula:

μ=Average±\frac{t*s}{\sqrt{n} }

Where:

t=t student constant with 95 % of confidence and 5 data=2.78

μ= 0.79  ±  \frac{2.78*0.0359}{\sqrt{5} }

upper limit:  0.84

lower limit: 0.75

If we compare the limits of the value obtanied by the method (Figure 1 Red line) with the reference material (Figure 1 blue line) we can see that the values obtained by the method are within the values suggested by the reference material. So, it's method is accurate.

7 0
3 years ago
Which describes the state at which products form at the same rate as reactants?
Ede4ka [16]
Products develop much faster than regular reactants
4 0
3 years ago
Where are the alkali metals, the alkaline earth metals, the halogens, and the noble gases located on the periodic table?
ivolga24 [154]
The Alkali Metals- (Group 1A)can be found (excluding hydrogen) in the first column of the periodic table. They all have 1 valence electron and tend to form +1 cations when forming Ionic bonds with non metals. 

The Alkali Earth Metals: (Group 2A) can be found in the second column/group on the periodic table. These elements form +2 positively charged cations when forming Ionic bonds with non metals. They also all have 2 valence electrons. 

The Halogens: are the elements that make up the second to last group on the periodic table. These elements include Chlorine, Fluorine, Bromine, Iodine, and Astatine. These elements have 7 valence electrons. The usually form a -1 charged anion when forming ionic bonds with metals. 

The Noble gases: the very last group on the periodic table. All these elements have 8 valance electrons. Due to the octet rule these atoms are already very stable and rarely react with other elements. 

3 0
3 years ago
Im completely finish why is it at 99.5 instead of 100??
lesya692 [45]

Answer:

because u need one more assianment before it becomes 100

Explanation:

7 0
3 years ago
Which is the highest reactive non metal
Stells [14]

Phosphorus I think not so sure

6 0
3 years ago
Read 2 more answers
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