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How to correctly answer the score application questions
Answer the score application questions, to analyze
At the same time, the bus and the truck run in opposite directions from the midpoint of a and B. one hour later, the bus arrives at a place and the truck leaves B place
2 ——
two
There are 42 kilometers left. It is known that the speed of freight cars is 3 / 5 of that of passenger cars. How many meters is the distance between the two places?
The speed of freight car is 3, and that of passenger car is 5
That is, 42 / (5-3) = 21 (km) (the amount of a portion)
21 times (5 + 5) = 210 km
1. There are three kinds of diatomic molecules formed by an element a, and their molecular weights are 158, 160 and 162 in turn. The weight ratio of these three kinds of molecular substances is 5:4:3. The following formula can be obtained: 1. The atoms of various isotopes of this element? 2. The atomic number ratio of various isotopes of this element?
2. Chlorine has two kinds of atoms, 35Cl and 37Cl. Their relative atomic mass are 34.97 and 36.97 respectively. Their atomic percentages in nature are 75% and 25% respectively
The results are as follows: 1)
2) Approximate relative atomic mass of chlorine
3) 37Cl
3. It is known that the approximate relative atomic mass of chlorine is 35.5. How many grams of 35Cl is contained in 50 grams of NaCl which is composed of 23Na, 35Cl and 37Cl?
1.(1)Br-79,Br-81
(2)(5*2+4*1):(4*1+3*2)=14:10=7:5
2.(1)34.97*75%+36.97*25%=35.47
(2)35.5
(3)36.97*25%/35.47*100%=26.1%
3.35x+37(1-x)=35.5
x=0.75,1-x=0.25
35Cl in 50g NaCl = 50 / 58.5 * 0.75 * 35 = 22.4g
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