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STALIN [3.7K]
3 years ago
7

in Analytical chemistry laboratory. Nickle(ppm)in water sample estimated by two different students was as ,student 1 (25 24 24 2

4 24 28 26 ) and student 2 (24 25 24 24 25 25 ), if the true valude on Nickle in water was 20 ppm estimate the precision and accuracy of both students
Chemistry
1 answer:
frosja888 [35]3 years ago
6 0

Answer:

Answers are in the explanation

Explanation:

Precision and accuracy are both statistical concepts. Precision is about how close are the measured values to each other. Accuracy is closeness of the measured values to a specific value or reference value.

There are many ways to calculate precision and accuracy, one is stimating precision as <em>Relative Uncertainty </em>and accuracy as <em>Relative Error.</em>

Formulas are:

Relative Uncertainty: Standard desviation /  Measured value.

Relative Error: Measured Value - Expected Value / Expected value

<em>Measured value is the aveage of the values.</em>

<em />

For student 1:

Mean = 25

Standard desviation = 1.5275

Relative Uncertainty: 1.5275 /  25

Relative Uncertainty: 0.061

Relative Error: 25 - 20 / 20

Relative Error: 0.25

For student 2:

Mean = 24.5

Standard desviation = 0.5477

Relative Uncertainty: 0.5477 / 24.5

Relative Uncertainty: 0.02

Relative Error: 24.5 - 20 / 20

Relative Error: 0.225

<em>As the student 2 has a low Relative error and uncertainty, you can say student 2 is more accurate and precise</em>

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How many atoms are there in 8.88 g Si?
Mariana [72]

Answer:

\boxed {\boxed {\sf 1.90 \times 10^{23} \ atoms \ Si}}

Explanation:

We are asked to find how many atoms are in 8.88 grams of silicon.

<h3>1. Grams to Moles </h3>

First, we convert grams to moles. We use the molar mass or the mass of 1 mole of a substance. These values are found on the Periodic Table as they are equal to the atomic masses, but the units are grams per mole instead of atomic mass units.

Look up silicon's molar mass.

  • Si:  28.085 g/mol

We will convert using dimensional analysis. Set up a conversion factor with the molar mass.

\frac { 28.085 \ g \  Si}{1 \ mol \ Si}

We are converting 8.88 grams of silicon to moles, so we multiply by this value.

8.88 \ g \ Si *\frac { 28.085 \ g \  Si}{1 \ mol \ Si}

Flip the fraction so the units of grams of silicon cancel.

8.88 \ g \ Si *\frac{1 \ mol \ Si} { 28.085 \ g \  Si}

8.88  *\frac{1 \ mol \ Si} { 28.085 }

\frac {8.88} { 28.085 } \ mol \ Si

0.316183015845 \ mol \ Si

<h3>2. Moles to Atoms </h3>

Next, we convert moles to atoms. We use Avogadro's Number or 6.022 × 10²³. This is the number of particles (atoms, molecules, formula units, etc.) in 1 mole of a substance. In this case, the particles are atoms of silicon.

Set up another conversion factor.

\frac {6.022 \times 10^{23} \ atoms \ Si}{1 \ mol \ Si}

Multiply by the number of moles we calculated.

0.316183015845\ mol \ Si *\frac {6.022 \times 10^{23} \ atoms \ Si}{1 \ mol \ Si}

The units of moles of silicon cancel.

0.316183015845 * \frac {6.022 \times 10^{23} \ atoms \ Si}{1}

0.316183015845 * {{6.022 \times 10^{23} \ atoms \ Si}

1.90405412 \times 10^{23} \ atoms \ Si

<h3>3. Significant Figures</h3>

The original measurement of 8.88 grams has 3 significant figures, so our answer must have the same.

For the number we calculated, that is the hundredth place. The 4 in the thousandth place tells us to leave the 0 in the hundredth place.

1.90 \times 10^{23} \ atoms \ Si

<u>8.88 grams of silicon contains 1.90 ×10²³ atoms of silicon.</u>

6 0
3 years ago
Which types of reactions would result in the production of gas?
mylen [45]

Answer:

farts

Explanation:

5 0
2 years ago
Define/Differentiate between a physical property and a chemical property?
irga5000 [103]

Answer:

A physical property is an aspect of matter that can be observed or measured without changing it. A chemical property may only be observed by changing the chemical identity of a substance.

Explanation:

i found a table that might be able to help u

4 0
3 years ago
You are carrying out an experiment in the lab to study the glycolysis pathway. To do this, a liver extract (which is capable of
Virty [35]

Answer:

When C1 is labeled in glucose, it ends up in the methyl group of pyruvate.

Aldolase cleaves a hexose into two trioses.

[See the image attached].

Asterisk indicates the label.

When C1 is labeled in glucose, it ends up in the carboxyl group of pyruvate.

5 0
3 years ago
A closed container holds 2.0 moles of CO2 gas at STP. How many moles of oxygen can be placed in a container of the same size at
PilotLPTM [1.2K]

Answer: 2 moles

Explanation:

STP is Standard Temperature and Pressure. That means the pressure is 1.00 atm and the temperature is 273K. Since the oxygen is placed in the same container, we can use Ideal Gas Law to figure out what container the CO₂ used.

Ideal Gas Law: PV=nRT

P=1.00 atm

n=moles

R=0.08206 Latm/Kmol

T=273K

CO₂

V=\frac{nRT}{P}

V=\frac{(2.0 mol)(0.08206Latm/Kmol)(273K)}{1.00atm}

V=44.8L

Since we know that CO₂ has a 44.8 L container, we can use that to find the moles of oxygen.

n=\frac{PV}{RT}

n=\frac{(1.00atm)(44.8L)}{(0.08206Latm/Kmol)(273K)}

n=1.99=2mol

There are 2 mol of oxygen.

5 0
3 years ago
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