8-2 divided by (- 4) - 1 / 8

8-2 divided by (- 4) - 1 / 8

8-2³/(-4)³-1/8
=8+8/64-1/8
=8+1/8-1/8
=8

What is 2 + 3 * [- 12] - 100

Original formula = 2-36-100 = - 132

Nine divided by (one-third x-three-quarters) is thirty-six

9÷(1/3x-3/4)=36
9=36*(1/3x-3/4)
9=12x-27
12x=36
x=3

Three fourths divided by x equals five twelfth

3/4x=5/12
x=5/12*4/3=5/9

3.7×15+21×4.5

It's 150

What does stoichiometry mean?

The stoichiometric number is actually the balance of the equation here. If the equation is balanced by the undetermined coefficient method, the number obtained is its coefficient, that is, the stoichiometric number. The relationship between the ratio of stoichiometric number and the number of particles, the quantity ratio of matter, the volume ratio of gas, the ratio of reaction rate, etc

Find the stoichiometric ratio
It is known that the mass ratio in the reaction is 2:3 and the relative molecular mass ratio is 1:4. The stoichiometric ratio of the two is calculated

From the mass / relative molecular mass = stoichiometry
The stoichiometric ratio is 2 / 1: (3 / 4) = 8:3

Stoichiometric ratio = what ratio
The number in front of the thermochemical formula
What ratio =. =. ==
Learning more makes you confused
Two don't seem the same
Is it related to volume ratio?

The ratio of the number of particles to the amount of matter in the reaction
When the standard conditions are gas is the volume ratio, solid liquid is not necessarily true

Find the stoichiometric number
In the following reaction, the stoichiometric numbers B and D are: axo4 - + by - + CH + = = = = DX ^ 2 + + ey2 + 8H2O
A.5,6
B.10,2
C.6,2
D.10,5

B
According to the conservation of oxygen, a = 2, according to the conservation of hydrogen, C = 16
According to charge conservation: 16-2-b = 2D
14-b==2d

Who can exemplify the usage of "difference method" in chemical calculation
It is helpful for the responder to give an accurate answer

Difference method
The difference method is based on the fact that the "difference" (solid mass difference, solution mass difference, gas volume difference, gas mass difference, etc.) before and after chemical reaction is directly proportional to the change of reactants or products
In this method, the "difference" is regarded as a term at the right end of the chemical equation, and the known difference (actual difference) is listed in proportion to the corresponding difference (Theoretical Difference) in the chemical equation. Other solving steps are exactly the same as those in the chemical equation
The key to solve problems with difference method is to find out the theoretical difference correctly
The difference method is widely used in chemical calculation, among which the mass difference method and volume difference method are more common
The application conditions of difference method are as follows
(1) Incomplete reaction or residue
In this case, the difference reflects the actual reaction and eliminates the influence of unreacted substances on the calculation
(2) There is a difference before and after the reaction, and the difference is easy to get. This is the premise of using the difference method. Only when the difference is easy to get, the difference method is fast, otherwise, other methods should be considered
Example 1: put a small piece of Na into 50 g FeCl3 solution, after the reaction is complete, filter and get 45.9 g of brown yellow solution, then the mass of Na input is
A、4.6g B、4.1g C、6.9g D、9.2g
[resolution] the following reaction occurs when Na is put into FeCl3 solution
6Na+2FeCl3+6H2O=6NaCl+2Fe(OH)3↓+3H2↑
If 2mol FeCl3 reacts with 6mol H2O, 6mol NaCl is formed, and the mass of solution is reduced by 82G. At this time, 6mol Na takes part in the reaction;
If the mass of the solution is reduced by 4.1G, the Na and mass of the reaction should be 0.3mol and 6.9g respectively
Example 2. Under the same temperature and pressure, the total weight of a bottle filled with O2 is 116g, the total weight of a bottle filled with CO2 is 122g, and the total weight of a bottle filled with a gas is 114g, then the relative molecular weight of the gas is ()
A、28 B、60 C、32 D、14
[analysis] from "under the same temperature, pressure and volume, the mass ratio of different gases is equal to their molar mass ratio", it can be seen that in this problem, the difference of gas mass is directly proportional to the difference of formula quantity. Therefore, the mass of the bottle can be calculated directly from the proportional formula without calculating the mass of the bottle
(122-116) / (44-32) = (122-114) / (44-m (gas))
So the answer is (a)