The development of chemistry has made a lot of contributions to improve the quality of human life. Please give two examples in daily life to illustrate

The development of chemistry has made a lot of contributions to improve the quality of human life. Please give two examples in daily life to illustrate

Clothes: chemical fiber fabrics make clothes colorful in color and texture
Food: the use of food additives and preservatives is a growing variety of food
Housing: the use of new materials makes housing more environmentally friendly and comfortable
Travel: the development of alloy and rubber products makes travel convenient and fast
Use: the successive production of various materials makes the various tools we use more dexterous and portable

Difficult problems in chemical calculation
At a certain temperature, divide 1000 g of 18% substance a solution into two equal parts
1) Take one part of the solution, evaporate 60g of water, and 2.5G crystals (excluding crystal water) will precipitate. If another 60g of water is evaporated, how many grams of crystals will precipitate? (keep the temperature unchanged before and after)
2) Add the solute to the other portion and calculate the maximum concentration of the solution?

1000 g of 18% solution of substance A is divided into two equal parts
each
Mass of solvent (water) = 500 * 82% = 410g
Mass of solute (a) = 500% 18% = 90g
60g of water was evaporated, and 2.5G of crystal (without crystal water) was precipitated
It indicates that the remaining solution is saturated solution
Mass of solvent (water) = 410-60 = 350g
Mass of solute (a) = 90-2.5 = 87.5
The saturation of this temperature can be calculated
350----87.5
100----25
（1）60-----15g
15g crystal precipitation
(2) The concentration of saturated solution is the highest
（25/125）*100%=20%

A difficult problem in chemical calculation
The gravimetric method for the determination of phosphorus is to add ammonium molybdate solution to the solution containing HPO4 & sup2; - (4 in the lower corner 2 and negative sign in the upper corner) and acidify it to form a colored ammonium molybdate precipitation {(NH4) 3 [po4.12moo3]} (numbers 3 and 4 are small, 12 is large)
Write out the equation of ion reaction in solution
2 if the minimum mass accurately measured by the molecular balance is 50mg, what is the minimum mass of phosphorus that can be measured according to the given accuracy
3 mghpo4 (small four) is also precipitation, assuming that this method can also be used to determine the content of phosphorus. Which of these two methods is more accurate? Why?

1. Ion equation:
HPO42-＋12MoO42-＋23H+＋3NH4+＝＝(NH4)3[PO4·12MoO3]↓＋12H2O
*This equation can be written according to the meaning of the question, but I think that in acidified solution, hpo42 - should be written as h3po3
2. The molecular balance is used to measure the mass of ammonium molybdophosphate precipitation in the experiment, so the minimum mass of ammonium molybdophosphate can be measured as 50mg, that is 0.05g
66 × 10 ^ - 5mol,
If there is one p atom in ammonium phosphomolybdate, then n (P) = 2.66 × 10 ^ - 5mol m (P) = 0.826mg
3. I'm not sure about the third question. I think the ammonium molybdate method is more accurate. I need to check some data. Maybe the KSP of mghpo4 is larger than that of ammonium molybdate, and the precipitation is not as complete as that of ammonium molybdate, so it is not as accurate as that of ammonium molybdate method

Xiaohua wants to determine the mass fraction of copper in Cu Zn alloy and Cu Ag alloy. The laboratory only provides a bottle of dilute sulfuric acid without mass fraction indicated and necessary instruments___ (2) Xiaohua takes 32.5g of the alloy powder and reacts with enough sulfuric acid to produce 0.4g gas. The mass fraction of copper in the alloy is calculated

(1) The activity of copper is weaker than that of hydrogen and does not react with dilute acid. The activity of zinc is stronger than that of hydrogen and can react with dilute acid, so the mass fraction of copper can be determined by copper zinc alloy. The activity of silver is weaker than that of hydrogen and does not react with dilute acid, so the mass fraction of copper can not be determined by copper silver alloy

Difficult problems in chemical calculation
The latest treatment technology is to use nano oxygen deficient ferrite (mfe2ox, 3

x=3.5
SO2: 0.01% * 22400l = 2.24l, i.e. 0.1mol
ZnFe2OX + (2-X/2)SO2=ZnFe2O4 +(2-X/2)S
(177+16X)g (2-X/2)mol
93.2g 0.1mol
The solution is x = 3.5

It is known that a G mg Al alloy reacts with a sufficient amount of HCl solution to obtain the standard gas cl. what is the mass fraction of aluminum in mg Al alloy

Let the mass fraction of aluminum be w
m(Al)=awg
m(Mg)=a(1-w)g
Al-3/2H2 Mg-H2
(aw/27)*3/2+a(1-w)/24=c/22.4
The solution is w = 3.2c/a-3

The application of stoichiometry in the laboratory, all the formulas,

1. It is necessary to define the basic calculation formula
(1) N = m / m, n is the amount of substance (mol), M is the mass (g), M is the molar mass (g / mol)
(2) N = n / Na, n is the number of particles, Na is the additionalderot constant
(3) N = V / VM, V is the volume of gas (L), VM is the molar volume of gas (L / mol) under certain conditions, VM = 22.4l/mol under standard conditions
(4) N = CV, C is the concentration of solute in solution (mol / L), V is the volume of solution (L)
2. Know and be proficient in common conversion and deduction formulas
(1) Conversion between mass concentration (c) and mass fraction (W)
C = 1000 DW / m, D is the density of solution (g / cm3), M is the molar mass of solute (g / mol)
(2) Conversion between mass fraction (W) and solubility (s) of saturated solution
w=s/(100+s)
(3) Under the same condition, the volume ratio of gas = the mass ratio of matter = the molecular number ratio of gas
V(A):V(B)=n(A):n(B)=N(A):N(B)
(4) Under the same condition, the ratio of gas density = molar mass = relative molecular mass
d(A):d(B)=M(A):M(B)=Mr(A):Mr(B)
Therefore, if the relative density of a gas to hydrogen is 16, that is, the MR of the gas is 16 × 2 = 32
This one is often used
Other, may also have, but not very useful, in addition, there is no need to recite all, remember the above several basic

The specific steps of using chemical cross method? And give examples
What is the ratio after subtraction? Can it only be used for density?

Introduction to the principle and application of chemical cross method cross method can be used to calculate the concentration of solution, such as dilution, concentration or mixing of solution. Using this method, the problem-solving process is simple, fast and correct

How to use the cross method in chemical calculation?
Its scope of application and the meaning of the letters below
Let the upper left corner of the intersection be a, the lower left corner be B, the middle corner be C, and the ratio be M1 / m2

1、 This is a method to write the chemical formula of a substance by combining valence. It is suitable for compounds composed of two elements or two groups. Its principle is based on the combining valence Law: the algebraic sum of the total number of positive valence and the total number of negative valence is 0 or the absolute value of the total number of positive valence and the total number of negative valence is equal

Application of stoichiometry in experiment
The mixture of Na2O and Na2O2 is produced by burning sodium in air. 74.8g of the combustion product is dissolved in water to make 1000ml solution. 10ml of the solution is neutralized with 1mol / L hydrochloric acid and 20ml of dehydrochloride. Therefore, the mass fraction of Na2O in the product is about ()
A、16.6%
B、20%
C、80%
D、78.4%

Take 74.8g of the combustion product and dissolve it in water to make 1000ml solution, take out 10ml, neutralize it with 1mol / L hydrochloric acid, and use 20ml de hydrochloric acid. The concentration of sodium hydroxide solution is 1 * 20 / 10 = 2mol / L
The mass of sodium hydroxide in 1000ml solution is 1 * 2 = 2mol
Suppose that 74.8g of combustion product contains XG of sodium oxide and reacts with water to form y-mole of sodium hydroxide, and 74.8-xg of sodium peroxide reacts with water to form 2-mole of sodium hydroxide
Na2O+H2O=2NaOH
62---------------2
X----------------Y
2X=62Y
2Na2O2+2H2O=4NaOH+O2
156-----------------4
74.8-X---------------2-Y
156*(2-Y)=4*(74.8-X)
The solution is x = 12.4 G
The mass fraction of Na2O in the product is about 12.4 / 74.8 = 16.6%
A is right