Chemical Reactions
Chemical changes take place when molecules or elements interact with other elements or molecules to form new chemical compounds. In order for a reaction to take place between molecules and or atoms, these molecules must come into contact with each other.
An example of a chemical reaction can be shown by the reaction of ammonia with hydrogen chloride to form ammonium chloride. This reaction is usually shown by a shorthand method called a chemical equation. The chemical equation for this reaction is...
NH3 + HCl � NH4Cl
This equation does not clearly show what has happened. In order for these two molecules to react, the pair of electrons on nitrogen must collide with the hydrogen atom of the hydrogen chloride on the side exactly opposite of the chlorine atom.
This collision must not only be precise as to the angle of the collision, it must have enough energy to break the bond between the hydrogen atom and the chlorine atom and form a new bond between the hydrogen atom and the nitrogen atom. Energy is released when a bond is formed. If all of these requirements are met, a reaction occurs forming a new compound.

The rate of a chemical reaction depends on all of the above factors. The reaction rate is measured by the change in concentration of one of the reactants or products over a measured period of time.
If some reaction condition is changed, the reaction rate will be changed.
Reaction coordinate diagrams are used to visualize the energy changes in chemical reactions. Some initial energy must be applied to any reaction in order to get the reaction started. This energy is called the energy of activation Ea.
If a reaction releases more energy than it takes to keep it going, it is called an exothermic reaction.

If a reaction requires a constant application of energy to keep it going, it is called an endothermic reaction.

A catalyst is something that, when added to a chemicalreaction, will increase the reaction rate without undergoing a permanent change. Although it appears that only Ea is lowered for a catalyzed reaction, the actual reaction pathway must change due to the involvement of the catalyst with the reactants. The energy released for the reaction remains the same. Catalysts are used extensively in biochemical reactions in order to decrease the energy demands for the animal or plant.

Matter can neither be gained nor lost in a chemical reaction. The number and type of atoms in the reactants must exactly equal the number and types of atoms in the products. The arrangement of the atoms will be different because new compounds are formed. Therefore, we must balance chemical equations with respect to the numbers of all of the atoms that are involved in the reaction.
Answer: Yes, two objects may have the same volume while having different masses. The object with a greater mass will be the one that contains more matter.
Explanation: Mass and volume are two different properties of matter. Mass is defined as the amount of matter that a body has. Volume is defined as the amount of space that a body occupies. Density is the property that relates mass with volume as
and is defined as the amount of matter that exists in a certain amount of space.
Because mass and volume are independent from each other, we can say that two objects can have different masses and have the same volume.
<u>For example</u>, imagine two identical containers that weigh the same and that are capable of containing a volume of 1 liter each. Then, one of the containers is filled with water, while the other one is filled with mercury. In this case the volume of the water and the volume of the mercury will be the same: 1 liter, however, if we weigh the containers again, we will find that the one that has mercury is heavier than the one that has water. This is due to the density of mercury being higher than the density of water. In other words, 1 liter of mercury provides more mass than the mass provided by 1 liter of water.
Then, according to the definition of mass, the object that contains more matter will be the one that has more mass, in the case of our example, that would be the liter of mercury.
Answer:
noun. the composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years. a region or area characterized by a given climate: to move to a warm climate.
Explanation:
Answer:
The concentration the student should write down in her lab is 2.2 mol/L
Explanation:
Atomic mass of the elements are:
Na: 22.989 u
S: 32.065 u
O: 15.999 u
Molar mass of sodium thiosulfate, Na2S2O3 = (2*22.989 + 2*32.065 + 3*15.999) g/mol = 158.105 g/mol.
Mass of Na2S2O3 taken = (19.440 - 2.2) g = 17.240 g.
For mole(s) of Na2S2O3 = (mass taken)/(molar mass)
= (17.240 g)/(158.105 g/mol) = 0.1090 mole.
Volume of the solution = 50.29 mL = (50.29 mL)*(1 L)/(1000 mL)
= 0.05029 L.
To find the molar concentration of the sodium thiosulfate solution prepared we use the formula:
= (moles of sodium thiosulfate)/(volume of solution in L)
= (0.1090 mole)/(0.05029 L)
= 2.1674 mol/L
