The state (phase) of the compounds can be expressed in the chemical equation. This is done by placing the correct label on the right hand side of the formula. There are only four labels that can be used:
(g) for gaseous compounds
(l) for liquids
(s) for solid compounds
(aq) for an aqueous (water) solution
To show that heat is needed for a reaction, a Greek delta (
) is placed above the arrow.
You may remember from
Physical and chemical change that energy cannot be created or destroyed during a chemical reaction but it may change form. In an exothermic reaction,
H is less than zero and in an endothermic reaction,
H is greater than zero. This value is often written at the end of a chemical equation.
Solid zinc metal reacts with aqueous hydrochloric acid to form an aqueous solution of zinc chloride (
)and hydrogen gas. Write a balanced equation for this reaction.
The reactants are zinc (
) and hydrochloric acid (
). The products are zinc chloride (
) and hydrogen (
).
You will notice that the zinc atoms balance but the chlorine and hydrogen atoms don't. Since there are two chlorine atoms on the right and only one on the left, we will give
a coefficient of 2 so that there will be two chlorine atoms on each side of the equation.
When you look at the equation again, you will see that all the atoms are now balanced.
In the initial description, you were told that zinc was a metal, hydrochloric acid and zinc chloride were in aqueous solutions and hydrogen was a gas.
Balance the following equation:
In this example, the first two steps are not necessary because the reactants and products have already been given.
With a complex equation, it is always best to start with atoms that appear only once on each side i.e.
,
and
atoms. Since the
atoms already balance, we will start with
and
atoms. There are two
atoms on the right and one on the left. We will add a second
atom by giving
a coefficient of two. There are two
atoms on the left and one on the right. To balance the
atoms,
will be given a coefficient of two. The equation now looks as follows:
,
and
atoms balance, but
and
atoms do not. There are six
atoms and ten
atoms on the left, and five
atoms and eight
atoms on the right. We need to add one
atom and two
atoms on the right to balance the equation. This is done by adding another
molecule on the right hand side. We now need to check the equation again:
The equation is now balanced.
The following video explains some of the concepts of balancing chemical equations.
Khan academy video on balancing chemical equations
Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
