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4 years ago

There are ____ main groups in the modern periodic table of elements

1 answer:

5 0

There are 18 numbered groups in the periodic table, and the f-block columns (between groups 3 and 4) are not numbered. The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms (i.e., the same core charge), as most chemical properties are dominated by the orbital location of the outermost electron. There are three systems of group numbering. The modern numbering group 1 to group 18 is recommended by the International Union of Pure and Applied Chemistry (IUPAC). It replaces two older naming schemes that were mutually confusing. Also, groups may be identified by their topmost element or have a specific name. For example, group 16 is variously described as the oxygen group and as the chalcogens.

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A 2.300×10−2 m solution of nacl in water is at 20.0∘c. the sample was created by dissolving a sample of nacl in water and then b

lilavasa [31]

The given question is incomplete. The complete question is as follows.

A 2.300×10−2 m solution of nacl in water is at 20.0∘c. the sample was created by dissolving a sample of nacl in water and then bringing the volume up to 1.000 l. it was determined that the volume of water needed to do this was 999.4 ml . the density of water at 20.0∘c is 0.9982 g/ml.

Calculate the molality of the salt solution.

Express your answer to four significant figures and include the appropriate units.

Explanation:

Molality is defined as the number of moles present in kg of a solvent.

Mathematically, Molality = $\frac{\text{moles of solute}}{\text{mass of solvent}}$

Also,

Mole of solute = Molarity of solute x Volume of solution

= (0.0230 M) x (1.000 L) = 0.0230 mol of solute

Therefore, mass of solvent will be as follows.

$999.4 mL \times (\frac{0.9983 g}{1 mL})$

= 997.7 g

= 0.9977 kg (as 1 kg = 1000 g)

Therefore, we will calculate the molality as follows.

Molality = $\frac{0.0230 mol}{0.9977 kg}$

= 0.02306 mol/kg

thus, we can conclude that molality of the given solution is 0.02306 mol/kg.

8 0

3 years ago

Suppose that you obtain 1.0 g of isopentyl acetate from reacting 1.0 mL of acetic acid with 1.0 mL of isopentyl alcohol. Calcula

Elden [556K]

Answer:

83.72%

Explanation:

The equation of of Reaction is given below;

CH3COOH + C5H11OH ------> CH3COOC5H11 + H2O. --------------(1).

The equation (1) shows that one mole of acetic acid react with one mole of isopentyl alcohol to give one mole of isopentyl acetate and one mole of water.

RATIO===> 1 : 1 ------> 1 : 1.

We are given 1.0 mL of acetic acid and 1.0 mL of isopentyl alcohol.

===> Things to know: The density of acetic acid = 1.05 g/cm^3 and the density of isopentyl alcohol= 0.809 g/cm^3, 1 mL = 1 cm^3, molar mass of isopentyl alcohol = 88.179 g/mol.

So, the density of acetic acid = 1.05 g/mL and the density of isopentyl alcohol= 0.809 g/mL.

Therefore, mass of acetic acid;

= 1.0 mL acetic acid ×( 1.05 g/ mL).

= 1.05 g acetic acid.

Mass of isopentyl alcohol= 1.0 mL × 0.809 g/mL = 0.809 grams isopentyl alcohol.

Since one mole of each reactants formed the product, we have to find the limiting reagent. This is done by converting the mass into moles.

Hence, for acetic acid; the number of moles = mass/molar mass.

===> 1.05 grams of acetic acid/ 60.052 g/mol.

===> 0.017485 moles acetic acid.

For isopentyl alcohol; 0.809/ 88.179 grams per mol.

==> 0.0091745 mol isopentyl alcohol.

We can see that isopentyl alcohol is the limiting reagent. So, 0.0091745 mole isopentyl alcohol will produce 0.0091745 mol isopentyl acetate.

Hence, the mass of isopentyl acetate= number of moles × molar mass= 0.0091745 × 130.19 grams per mol.

==> 1.19 grams isopentyl acetate.

FINAL STEP: calculating the percent yield. The actual yield is 1.0 g, theoretical yield = 1.19 grams

Percent yield = actual yield/ theoretical yield × 100.

Percent yied;

= 1.0 grams/ 1.19 grams × 100.

= 83.72 %.

8 0

4 years ago

The Hope diamond has a mass of 44.0 carats and a density of 3.51 g/cm3. What is the volume of the Hope diamond? (Hint: 1 carat =

Georgia [21]

Q=44.0 ct
p=3.51 g/cm³
Δq=0.200 g/ct

m=q×Δq

v=m/p=q×Δq/p

v=44.0×0.200/3.51≈2.5 cm³

C. 2.5 cm³

7 0

3 years ago

In a competition, an athlete threw a flying disk 139 meters through the air. While in flight, the disk traveled at an average sp

sesenic [268]

Answer:

10.69 s

In a competition, an athlete threw a flying disk 139 meters through the air. While in flight, the disk traveled at an average speed of 13.0 m/s. How long did the disk remain in the air? Answer: 10.69 s Page 2 8.

Explanation:

3 0

3 years ago

Which of the answer choices correctly explains how the law of conservation of energy is fulfilled during an exothermic reaction?

Anarel [89]

Based on my (limited) knowledge, I would say the answer is:

In an exothermic reaction, the products have less potential energy than the reactants, so energy is absorbed from the surroundings during the reaction.

Hope this helps :)

6 0

4 years ago

Read 2 more answers