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4 years ago

An unknown substance undergoes a chemical change that gives off heat. What can you tell me about this substance?

Chemistry

2 answers:

marin [14]4 years ago

7 0

On a molecular level there is a lot of movement which in turn is the reason why heat is generated.

madam [21]4 years ago

3 0

Explanation:

A chemical reaction in which heat is absorbed by the reactant molecules is known as an endothermic reaction.

For example, $A + B + Heat \rightarrow AB$

On the other hand, a chemical reaction in which heat energy is released by the reactant molecules is known as an exothermic reaction.

For example, $A + B \rightarrow AB + Heat$

Thus, we can conclude that when an unknown substance undergoes a chemical change that gives off heat then it means earlier the substance has more heat energy but after the chemical change there occurs a decrease in its heat energy because some of the heat has been released by it.

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It is water flows through this type of soil

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3 years ago

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What was the impact of the british clean air act of 1956

Sladkaya [172]

The correct answer in here is: Limited the burning of soft coal. Some reasons for that are that when Britain was the workshop of the world its coal consumption increased from around 10 million tons per annum in 1800 to almost 200 million tons in 1950 and also that Coal smoke was linked to very high death rates from respiratory diseases such as bronchitis, killing between 800,000 and 1.4 million people in the period 1840-1900.

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3 years ago

When of a certain molecular compound X are dissolved in of benzene , the freezing point of the solution is measured to be . Calc

puteri [66]

The question is incomplete. Here is the complete question.

When 2.10 g of a certain molecular compound X are dissolved in 65.0 g of benzene (C₆H₆), the freezing point of the solution is measured to be 3.5°C. Calculate the molar mass of X. If you need any additional information on benzene, use only what you find in the ALEKS Data resource. Also, be sure your answer has a unit symbol, and is rounded to 2 significant digits.

Answer: MM = 47.30 g/mol.

Explanation: There is a relationship between freezing point depression and molality. With this last one, is possible to calculate molar mass or molar weight of a compound.

Freezing Point Depression occurs when a solute is added to a solvent: the freezing point of the solvent decreases when a non-volatile solute is incremented.

Molality or molal concentration is a quantity of solute dissolved in a certain mass, in kg, of solvent. Its symbol is m and it's defined as

$m=\frac{moles(solute)}{kg(solvent)}$

Freezing point depression and molal are related as the following:

$\Delta T_{f}=K_{f}.m$

where

$\Delta T_{f}$ is freezing point depression of solution

$K_{f}$ is molal freezing point depression constant

m is molality

Now, to determine molar mass, first, find molality of the mixture:

$\Delta T_{f}=K_{f}.m$

$m=\frac{\Delta T_{f}}{K_{f}}$

For benzene, constant is 5.12°C/molal. Then

$m=\frac{3.5}{5.12}$

m = 0.683 molal

Second, knowing the relationship between molal and moles of solute, determine the last one:

$m=\frac{moles(solute)}{kg(solvent)}$

$mol(solute)=m.kg(solvent)$

mol(solute) = 0.683(0.065)

mol(solute) = 0.044 mol

The definition for Molar mass is the mass in grams of 1 mol of substance:

$n(moles)=\frac{m(g)}{MM(g/mol)}$

$MM=\frac{m}{n}$

In the mixture, there are 0.044 moles of X, so its molecular mass is

$MM=\frac{2.1}{0.044}$

MM = 47.30 g/mol

The molecular compound X has molecular mass of 47.30 g/mol.

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3 years ago

What is the molar mass of calcium sulfate (caso4):?

emmasim [6.3K]

CaSO4 - to find the molar mass, you add the element's mass number.

40.08 + 32.06 + (16x4)

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3 years ago

Paul has different spoons for cooking. He told Sue that he likes to stir hot food with a wooden spoon because it does not burn h

IceJOKER [234]

Answer:

Sue was not right as wood is not a heat conductor and will not allow heat to pass through the spoon thus keeping the hand safe. In a meatal spoon, heat can pass through and burn the hand as meatal is a good conductor of heat.

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3 years ago