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3 years ago

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 total pressure of multiple gases is 512 mmHg, and the pressure of oxygen gas is 332 mmHg and the pressure of carbon monoxide

deff fn [24]

Answer: 67 mmHg

Explanation:

According to Dalton's Gas Law, the total pressure of a mixture of gases is the sum of the pressure of each individual gas.

i.e Ptotal = P1 + P2 + P3 + .......

In this case,

Ptotal = 512 mmHg

P(oxygen) = 332 mmHg

P(carbon mono-oxide) = 113 mmHg

Remaining pressure (P3) = ?

To get P3, apply Dalton's Gas Law formula

Ptotal = P(oxygen) + P(carbon mono-oxide) + P3

512 mmHg = 332 mmHg + 113 mmHg + P3

512 mmHg = 445 mmHg + P3

P3 = 512 mmHg - 445 mmHg

P3 = 67 mmHg

Thus, the remaining pressure is 67 mmHg

5 0

3 years ago

When you apply 1000 joules of energy to 50 grams of water its temperature changes to 30 degrees . What was the initial temperatu

expeople1 [14]

Answer:

25.2°C

Explanation:

Given parameters:

Energy applied to the water = 1000J

Mass of water = 50g

Final temperature = 30°C

Unknown:

Initial temperature = ?

Solution:

To solve this problem, we use the expression below:

H = m c Ф

H is the energy absorbed

m is the mass

c is the specific heat capacity

Ф is the change in temperature

1000 = 50 x 4.184 x (30 - initial temperature )

1000 = 209.2(30 - initial temperature)

4.78 = 30 - initial temperature

4.78 - 30 = - initial temperature

Initial temperature = 25.2°C

7 0

3 years ago

Aspirin can be prepared from salicylic acid ( C 7 H 6 O 3 CX7HX6OX3), which has a molar mass of 138.12 g/mol, and acetic anhydri

pychu [463]

Answer: The theoretical yield of aspirin is 4.14 g

Explanation:

To calculate the moles :

$\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}$ $\text{Moles of salicylic acid}=\frac{3.20g}{138.12g/mol}=0.023moles$

mass of acetic anhydride = $density\times volume =1.082g/ml\times 3.71ml=4.01g$

$\text{Moles of acetic anhydride}=\frac{4.01g}{102.04g/mol}=0.039moles$

$C_9H_6O_3+C_4H_6O_3\rightarrow C_9H_8O_4+C_2H_3O_2$

According to stoichiometry :

1 mole of salycylic acid require 1 mole of acetic anhydride

Thus 0.023 moles of salycylic acid require= $\frac{1}{1}\times 0.023=0.023moles$ of acetic anhydride

Thus salycylic acid is the limiting reagent as it limits the formation of product and acetic anhydride is the excess reagent.

As 1 mole of salycylic give = 1 mole of aspirin

Thus 0.023 moles of salycylic acid give = $\frac{1}{1}\times 0.023=0.023moles$ of aspirin

Mass of aspirin = $moles\times {\text {Molar mass}}=0.023moles\times 180.15g/mol=4.14g$

Thus theoretical yield of aspirin is 4.14 g

4 0

3 years ago

A 34.53 ml sample of a solution of sulfuric acid, h2s04, reacts with 27.86 ml of 0.08964 m naoh solution. calculate the molarity

Gnoma [55]

The balanced equation between NaOH and H₂SO₄ is as follows
2NaOH + H₂SO₄ ---> Na₂SO₄ + 2H₂O
stoichiometry of NaOH to H₂SO₄ is 2:1
number of moles of NaOH moles reacted = molarity of NaOH x volume
number of NaOH moles = 0.08964 mol/L x 27.86 x 10⁻³ L = 2.497 x 10⁻³ mol
according to molar ratio of 2:1
2 mol of NaOH reacts with 1 mol of H₂SO₄
therefore 2.497 x 10⁻³ mol of NaOH reacts with - 1/2 x 2.497 x 10⁻³ mol of H₂SO₄
number of moles of H₂SO₄ reacted - 1.249 x 10⁻³ mol
Number of H₂SO₄ moles in 34.53 mL - 1.249 x 10⁻³ mol
number of H₂SO₄ moles in 1000 mL - 1.249 x 10⁻³ mol / 34.53 x 10⁻³ L = 0.03617 mol
molarity of H₂SO₄ is 0.03617 M

6 0

3 years ago

Plz I need help is the 2nd time I post this

pychu [463]

Answer:

2--->C

6---->E

3---->D

4--->A

5--->B

1---->F

Explanation:

I think so, sorry if its wrong.

8 0

2 years ago