Which of the following is a description of an exothermic reaction?

A. releases heat
B. reactants have less enthalpy than the products
C. ∆H is positive
D. gets cold

Answer:

The necklace is fake.

The necklace is made up of copper.

Explanation:

The following data were obtained from the question:

Mass of the necklace = 21.3 g

Volume of water = 5 mL

Volume of water + Necklace = 7.4 mL

To identify the composition of the necklace, we shall determine the density of the necklace.

This can be obtained as follow:

We'll begin by calculating the volume of the necklace. This can be obtained as shown below:

Volume of water = 5 mL

Volume of water + Necklace = 7.4 mL

Volume of Necklace =.?

Volume of Necklace = (Volume of water + Necklace) – (Volume of water)

Volume of Necklace = 7.4 – 5

Volume of Necklace = 2.4 mL

NOTE:

1 mL = 1 cm³

Therefore,

Volume of Necklace = 2.4 mL = 2.4 cm³

Finally, we shall determine the density of the necklace as follow:

Mass of the Necklace = 21.3 g

Volume of Necklace = 2.4 cm³

Density of Necklace =?

Density = mass /volume

Density = 21.3 / 2.4

Density = 8.87 g/cm³

Therefore, the density of the necklace is 8.87 g/cm³.

From the question given above, we were told Jacy bought a gold necklace.

But comparing the density of necklace to the densities given above the necklace is obviously made of copper material.

Therefore, Jacy bought a fake gold necklace.

Answer:

2.6 kJ/mol

Explanation:

Step 1: Given data

Step 2: Calculate ΔG°

We can calculate ΔG° using the following expression.

ΔG° = ΔH° - T × ΔS°

ΔG° = 40.7 kJ/mol - 350 K × 0.109 kJ/mol.K

ΔG° = 2.6 kJ/mol

The change in Gibbs free energy, ΔG for the water is 2.55 KJ/mol

From the question given above, the following data were obtained:

The Gibbs free energy, ΔG° can be obtained as illustrated below:

ΔG° = ΔH° – TΔS°

ΔG° = 40.7 – (350 × 0.109)

ΔG° = 40.7 – 38.15

ΔG° = 2.55 KJ/mol

Learn more about Gibbs free energy:

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Answer:

1.  31.25 mL

2.  1.98 g/L

3.  0.45 g/mL

Explanation:

For each of the problems, you need to perform unit conversions.  You need to use the information given to you to convert to a specific unit.

1.  You need volume (mL).  You have density (g/mL) and mass (g).  Divide mass by density.  You will cancel out mL and be left with g.

(50.0 g)/(1.60 g/mL) = 31.25 mL

2.  You are given grams and liters.  You need to find density with units g/L.  This means that you have to divide grams by liters.

(0.891 g)/(0.450 L) = 1.98 g/L

3.  You have to find density again but this time with units g/mL.  Divide the given mass by the volume.

(10.0 g)/(22.0 mL) = 0.45 g/mL

Answer:

This question appears to be incomplete

Explanation:

However, we know that one of the kinetic theories of gases is that gas molecules collide with one another and against the walls of the container (in which they are stored); hence exerting there pressure on the walls of this container.

Ideal gases are the most suitable for this theory because it's molecules are far apart and do not exert any attractive forces towards one another; hence it's molecules move "undisturbed" or "freely". For ideal gases, the average pressure exerted by by the gas molecules on the walls of the container can be calculated as

PV = nRT

Where P = pressure (in atmosphere, atm or kilopascal, KPa or millimeter mercury, mmHg)

V = volume (in liters)

n = number of molecules

R = ideal gas constant (8.3145 J·mol⁻¹·K⁻¹)

T = temperature (in kelvin)

Answer:

0.024951344877489 mole.

Explanation:

y

Answer:

A ; 20g of water has the least number of molecules

Explanation:

Here, we want to know which of the options represent the least number of molecules;

To calculate this, we are going to first calculate the number of moles using the formula below;

Number of moles = mass/molar mass

Then from the number of moles, we can calculate the number of molecules by multiplying the number of moles by 6.02 * 10^23 molecules

Let’s proceed;

a. That will be 20/18.02 = 1.1099 moles

1.1099 * 6.02 * 10^23 = 6.68 * 10^23 molecules

b. That will be 77/16.06 = 4.8 moles

4.8 * 6.02 * 10^23 = 2.89 * 10*24 molecules

c. That will be 68/42.09 = 1.62 moles

1.62 * 6.02 * 10^23 = 9.73 * 10^23 molecules

d. That will be 100/44.02 = 2.27 moles

2.27 * 6.02 * 10^23 = 1.37 * 10^24 molecules

e. That will be = 84/20.01 = 4.2 moles

4.2 * 6.02 * 10^23 = 2.53 * 10^24 molecules

From all the values obtained, the lowest is 20g of water

Answer:

Because both CaCl2 and CaBr2 both contain elements (Chlorine and Bromine) from the same group (group 7)

Explanation:

Elements are placed into different groups in the periodic table. Elements in the same group are those that have the same number of valence electrons in their outermost shell and as a result will behave similar chemically i.e. will react with other elements in the same manner.

Chlorine and Bromine are two elements belonging to group 7 of the periodic table. They are called HALOGENS and they have seven valence electrons in their outermost shell. Hence, when they form a compound with Calcium, a group two element, these compounds (CaCl2 and CaBr2) will possess similar properties because they have elements that are from the same group (halogen group).

The compounds of [tex]\rm CaCl_2[/tex] and [tex]\rm CaBr_2[/tex] have similar chemical properties as they are constituted of elements belonging to the same group.

The compounds with the elements belonging to the same group have similar chemical properties. It has been given that the chemical properties of elements have been dependent on the number of valence electrons.

The given compounds have been calcium chloride and calcium bromide. The calcium has been the same cation in the compounds however, the anions are different.

The anion Cl and Br both belongs to group 17 and have 7 valence electrons. Thus, the compounds have been possessing similar chemical properties.

Thus, calcium chloride and calcium bromide are more likely to have similar chemical properties as they have elements belonging to the same group.

For more information about chemical properties, refer to the link:

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Answer:The fishing way and how fast is going

Explanation:Because of the variables the fishing we will flow much more faster

Answer:

Density of 40 mL of liquid that has a mass of 20 g = 20 / 40 = 0.5 g / cc

Answer:

Density= mass/volume

Density= 20/40

Density= 0.5g/mL