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3 years ago

What does a high melting point temperature indicate about a substance?

1 answer:

5 0

Melting, or the change of physical states, is the change of distance between particles. In solid state, particles are closely packed together. Energy is required to separate them in order to make it become liquid or even gas.
When a substance has a high melting point, it means the intermolecular forces or the chemical bonds are strong and the particles are easily attracted to each other. Therefore, more energy is needed to overcome these forces. A higher temperature could provide such energy.
Elements are combined together by different kinds of bonds. Ionic bonds and metallic bonds are considered to be strong. Ionic compounds (eg. NaCl) and metals tend to have a high melting point. In covalent compounds, molecules are held by weak van der Waals’ force. Thus, covalent compounds (eg. most gases, like CO2) have a low melting point.
Yet, water molecules, which are covalent compounds, have a higher melting point than others. It is because water molecules are polar, which allows hydrogen bonds to form among molecules, keeping them close together. More energy is required to melt ice or boil water than normal covalent compounds.

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A serving of fish contains 50 g of protein and 4 g of fat . if protein has a caloric value of 4.0kcal/g and fat has 9.1 kcal/g ,

weqwewe [10]

Answer:

2.4x10² kcal

Explanation:

As the serving of fish contains 50g of protein that is 4.0kcal/g:

50g × (4.0kcal/g) = 200kcal

And in 4g of fat that is 9.1kcal/g:

4g × (9.1kcal/g) = 36.4kcal

That means the kcal of the serving are:

200kcal + 36.4kcal = 236.4kcal

In 2 significant figures: 2.4x10² kcal

I hope it helps!

8 0

3 years ago

How to get the density of this unknown liquid?

scoray [572]

Answer:

Measure the volume of water poured into a graduated cylinder, then place the object in the water and remeasure the volume. The difference between the two volume measurements is the volume of the object. Now simply divide the mass by the volume to calculate the density of the object.

3 0

3 years ago

Why is it necessary to know the temperature of the reactants and the products of a reaction in order to determine change in the

Crank

Answer:

Free Energy (G) can either increase or decrease for a reaction when the temperature increases. It depends on the entropy (S) change. The change in a quantity is represented by the Greek letter delta. ... Hence, when the temperature increases the numeric value of the free energy becomes larger.

Explanation:

6 0

3 years ago

Answer these please ASAP need help no idea how to do these

STALIN [3.7K]

Answer:

Explanation:

Cu:

Number of moles = Mass / molar masa

2 mol = mass / 64 g/mol

Mass = 128 g

Mg:

Number of moles = Mass / molar masa

0.5 mol = mass / 24 g/mol

Mass = g

Cl₂:

Number of moles = Mass / molar masa

Number of moles = 35.5 g / 24 g/mol

Number of moles = 852 mol

H₂:

Number of moles = Mass / molar mass

8 mol = Mass / 2 g/mol

Mass = 16 g

P₄:

Number of moles = Mass / molar masa

2 mol = mass / 124 g/mol

Mass = 248 g

O₃:

Number of moles = Mass / molar masa

Number of moles = 1.6 g /48 g/mol

Number of moles = 0.033 mol

H₂O

Number of moles = Mass / molar masa

Number of moles = 54 g / 18 g/mol

Number of moles = 3 mol

CO₂

Number of moles = Mass / molar masa

2 mol = mass / 124 g/mol

Mass = 248 g

NH₃

Number of moles = Mass / molar masa

Number of moles = 8.5 g / 17 g/mol

Number of moles = 0.5 mol

CaCO₃

Number of moles = Mass / molar masa

Number of moles = 100 g / 100 g/mol

Number of moles = 1 mol

Given data:

Mass of iron(III)oxide needed = ?

Mass of iron produced = 100 g

Solution:

Chemical equation:

F₂O₃ + 3CO → 2Fe + 3CO₂

Number of moles of iron:

Number of moles = mass/ molar mass

Number of moles = 100 g/ 56 g/mol

Number of moles = 1.78 mol

Now we compare the moles of iron with iron oxide.

Fe : F₂O₃

2 : 1

1.78 : 1/2×1.78 = 0.89 mol

Mass of F₂O₃:

Mass = number of moles × molar mass

Mass = 0.89 mol × 159.69 g/mol

Mass = 142.124 g

100 g of iron is 1.78 moles of Fe, so 0.89 moles of F₂O₃ are needed, or 142.124 g of iron(III) oxide.

Given data:

Number of moles of Al = 0.05 mol

Mass of iodine = 26 g

Limiting reactant = ?

Solution:

Chemical equation:

2Al + 3I₂ → 2AlI₃

Number of moles of iodine = 26 g/ 254 g/mol

Number of moles of iodine = 0.1 mol

Now we will compare the moles of Al and I₂ with AlI₃.

Al : AlI₃

2 : 2

0.05 : 0.05

I₂ : AlI₃

3 : 2

0.1 : 2/3×0.1 = 0.067

Number of moles of AlI₃ produced by Al are less so it will limiting reactant.

Mass of AlI₃:

Mass = number of moles × molar mass

Mass = 0.05 mol × 408 g/mol

Mass = 20.4 g

26 g of iodine is 0.1 moles. From the equation, this will react with 2 moles of Al. So the limiting reactant is Al.

Given data:

Mass of lead = 6.21 g

Mass of lead oxide = 6.85 g

Equation of reaction = ?

Solution:

Chemical equation:

2Pb + O₂ → 2PbO

Number of moles of lead = mass / molar mass

Number of moles = 6.21 g/ 207 g/mol

Number of moles = 0.03 mol

Number of moles of lead oxide = mass / molar mass

Number of moles = 6.85 g/ 223 g/mol

Number of moles = 0.031 mol

Now we will compare the moles of oxygen with lead and lead oxide.

Pb : O₂

2 : 1

0.03 : 1/2×0.03 = 0.015 mol

Mass of oxygen:

Mass = number of moles × molar mass

Mass = 0.015 mol × 32 g/mol

Mass = 0.48 g

The mass of oxygen that took part in equation was 0.48 g. which is 0.015 moles of oxygen. The number of moles of Pb in 6.21 g of lead is 0.03 moles. So the balance equation is

2Pb + O₂ → 2PbO

6 0

3 years ago

PLS HELP!

Nadya [2.5K]

Question 1

Fe(III) forms a chelate complex with salicylic acid which has purple color. therefore, when a solution is made either with salicylic acid or with aspirin having trae amount of salicylic acid in it, we see color formation in solution due to the resulting complex formed.

Question 2

The Fe(III) itself absorbs some light and gives an absorbance value for the solution. Therefore, it is necessary to blank the spectrophotometer with a Fe(III) solution prior to measurement of test solutions.

6 0

2 years ago