What is the only sure evidence for a chemical reaction?

You apply the same amount of heat to five grams of water and five grams of aluminum. The temperature of the aluminum increases m

Mashutka [201]

Specific heat is another physical property of matter. All matter has a temperature associated with it. The temperature of matter is a direct measure of the motion of the molecules: The greater the motion the higher the temperature:

Motion requires energy: The more energy matter has the higher temperature it will also have. Typicall this energy is supplied by heat. Heat loss or gain by matter is equivalent energy loss or gain.

With the observation above understood we con now ask the following question: by how much will the temperature of an object increase or decrease by the gain or loss of heat energy? The answer is given by the specific heat (S) of the object. The specific heat of an object is defined in the following way: Take an object of mass m, put in x amount of heat and carefully note the temperature rise, then S is given by

In this definition mass is usually in either grams or kilograms and temperatture is either in kelvin or degres Celcius. Note that the specific heat is "per unit mass". Thus, the specific heat of a gallon of milk is equal to the specific heat of a quart of milk. A related quantity is called the heat capacity (C). of an object. The relation between S and C is C = (mass of obect) x (specific heat of object). A table of some common specific heats and heat capacities is given below:

Some common specific heats and heat capacities: Substance S (J/g 0C) C (J/0C) for 100 g Air 1.01 101 Aluminum 0.902 90.2 Copper 0.385 38.5 Gold 0.129 12.9 Iron 0.450 45.0 Mercury 0.140 14.0 NaCl 0.864 86.4 Ice 2..03 203 Water 4.179 417.9

Consider the specific heat of copper , 0.385 J/g 0C. What this means is that it takes 0.385 Joules of heat to raise 1 gram of copper 1 degree celcius. Thus, if we take 1 gram of copper at 25 0C and add 1 Joule of heat to it, we will find that the temperature of the copper will have risen to 26 0C. We can then ask: How much heat wil it take to raise by 1 0C 2g of copper?. Clearly the answer is 0.385 J for each gram or 2x0.385 J = 0.770 J. What about a pound of copper? A simple way of dealing with different masses of matter is to dtermine the heat capacity C as defined above. Note that C depends upon the size of the object as opposed to S that does not.

We are not in position to do some calculations with S and C.

Example 1: How much energy does it take to raise the temperature of 50 g of copper by 10 0C?

Example 2: If we add 30 J of heat to 10 g of aluminum, by how much will its temperature increase?

Thus, if the initial temperture of the aluminum was 20 0C then after the heat is added the temperature will be 28.3 0C.

5 0

3 years ago

Kim Chemist proposes that increasing the proportion of butadiene in her glue formulation will make the glue stickier. Her propos

Sunny_sXe [5.5K]

Answer: option D) hypothesis

Explanation:

Kim proposal is an hypothesis, because it is an assumption that will ONLY be accepted as true (i.e becomes a theory) when butadiene successfully makes the glue stickier in several conducted experiments.

But, at the moment Kim proposal is an hypothesis.

7 0

4 years ago

what is the percent yield of titanium (II) oxide if 20.0 grams of titanium (II) sulfide is reacted with water? The actual yield

earnstyle [38]

Answer : The percent yield of titanium (II) oxide is, 142.5 % and the impurities could have caused the percent yield to be so high.

Explanation : Given,

Mass of titanium(II) sulfide = 20.0 g

Molar mass of titanium(II) sulfide = 79.9 g/mole

Molar mass of titanium(II) oxide = 63.9 g/mole

First we have to calculate the moles of titanium(II) sulfide.

$\text{ Moles of titanium(II) sulfide}=\frac{\text{ Mass of titanium(II) sulfide}}{\text{ Molar mass of titanium(II) sulfide}}=\frac{20.0g}{79.9g/mole}=0.2503moles$

Now we have to calculate the moles of titanium(II) oxide.

The balanced chemical reaction is,

$TiS+H_2O\rightarrow TiO+H_2S$

From the reaction, we conclude that

As, 1 mole of titanium(II) sulfide react to give 1 mole of titanium(II) oxide

So, 0.2503 mole of titanium(II) sulfide react to give 0.2503 mole of titanium(II) oxide

Now we have to calculate the mass of titanium(II) oxide.

$\text{ Mass of titanium(II) oxide}=\text{ Moles of titanium(II) oxide}\times \text{ Molar mass of titanium(II) oxide}$

$\text{ Mass of titanium(II) oxide}=(0.2503moles)\times (63.9g/mole)=15.99g$

To calculate the percentage yield of titanium (II) oxide, we use the equation:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield of titanium (II) oxide = 22.8 g

Theoretical yield of titanium (II) oxide = 15.99 g

Putting values in above equation, we get:

$\%\text{ yield of titanium (II) oxide}=\frac{22.8g}{15.99g}\times 100\\\\\% \text{yield of titanium (II) oxide}=142.5\%$

Hence, the percent yield of titanium (II) oxide is, 142.5 %

If the percent yields is greater than 100% that means the product of the reaction contains impurities which cause its mass to be greater than it actually.

5 0

3 years ago

Consider the reaction: AB As the reaction proceeds, the concentration of A drops from 0.625 M to 0.100 Min 11.6 seconds. What is

prisoha [69]

Answer:

0.045 M/s

Explanation:

Given:

Initial concentration of A = 0.625 M

Final concentration of A = 0.100 M

Total time taken for the change of concentration = 11.6 seconds

The average rate of reaction is calculated as:

= $\frac{\textup{Change in concentration of A}}{\textup{Time taken for the change}}$

on substituting the respective values, we get

= $\frac{0.625-0.100}{\textup{11.6}}$

or

The average rate of reaction = 0.045 M/s

3 0

3 years ago

Look at the diagram. Which shows the correct arrangement of electrons in a hydrogen molecule?

skelet666 [1.2K]

It’s diagram because hydrogen has one proton and you’re not talking about ions so it needs another electron to stable itself

8 0

3 years ago