Xueba, I beg you to go and escort him quickly!

Yue Pingting nodded, "Yeah! Yes! I looked at a few questions and was stunned."

Xu Heng, "For these two types of questions, the equation will be balanced."

"Let's talk about the simple balance first. The conservation of the number of electrons gained and lost is used here. It is basically divided into two steps. The first step is the conservation of charge,..."

"..."

As he was talking, many students around him turned their heads and looked over.

When Xu Heng finished speaking and raised his head, these students looked at Xu Heng and blinked their eyes.

Xu Heng, "???"

Yue Pingting stared blankly at the several methods Xu Heng said, and answered the questions seriously.

topic:

Cu2S+HNO3（稀）→Cu（NO3）2+H2SO4+NO↑+H2O

According to the fourth method Xu Heng said.

Yue Pingting finally answered it.

“你看看，是不是3、22、6、3、10、8！”

Xu Heng glanced down and nodded.

"One point is enough, you can consolidate and practice."

Yue Pingting, "Good!"

Xu Heng continued to swipe his phone.

Not long after, Yue Pingting felt that she had mastered it well, and didn't bother Xu Heng, so she continued to read her chemistry problems.

Girls' understanding of chemistry is relatively weak.

In this regard, it is indeed not as good as boys.

Coupled with her poor foundation, Yue Pingting struggled a bit when doing chemistry problems.

Xu Heng glanced at her.

"Why, after watching for so long, haven't you answered this multiple-choice question?"

Yue Pingting glanced at Xu Heng, and muttered, "It's a bit ambiguous...so..."

Xu Heng tapped Yue Pingting's little head.

"Don't be ambiguous, let me teach you!"

Yue Pingting immediately hugged her head and muttered softly to resist, "It's class, you are too much..."

For a noob like Yue Pingting.

Xu Heng is still willing to teach.

If it were someone else, he would refute you, because his own thinking and learning methods are deeply ingrained.

Some even get into the dead end.

Or, for the sake of face, become a bully!

After all, everyone has good grades and can come up with an answer. My method is very good. Why should I listen to you?

So what about your simplicity, anyway, the answer is right, just fine!

Xu Heng looked at the question.

The laboratory uses concentrated hydrochloric acid and manganese dioxide to react to produce chlorine gas. Which of the following statements is correct (the gas volume is measured under the standard) ()

A. If 0.4mol HCl is provided and MnO2 is excessive, 4.48L of chlorine gas can be produced

B. If 0.4mol HCl is provided and MnO2 is excessive, the number of transfer points must be 0.1mol

C. If 0.4mol HCl participates in the reaction, 2.24L of chlorine gas can be produced

D. If 0.4mol HCl is chlorinated, 2.24L of chlorine gas can be produced

Below the title, Yue Pingting has already listed the chemical formula.

Xu Heng was unambiguous, and said directly, "Hydrochloric acid produces chlorine gas. It also exhibits acidity and reducing properties. What is particularly annoying about this kind of acid is that in any equation for producing chlorine gas, there must be a word "concentrated" after this hydrochloric acid." !"

"One word is missing from your equation, remember, concentrated hydrochloric acid."

"In other words, if it's not strong, it won't react."

"Let's look at options, A and B, here is the offer, remember, this offer means that it will not respond if it is reflected, what does it mean?"

Yue Pingting replied, "If you provide so much, you may not use so much!"

Xu Heng nodded, "Yes, the actual consumption must be less than 0.4mol, so the chlorine gas produced must also be less than 0.1mol!"

"Look at the CD again, this side consumes 0.4mol..."

Yue Pingting became excited, "So it really consumed 0.4mol in total!"

Xu Heng, "That's right! So the result is really 0.1mol!"

"Okay, I'm done reading this side!"

"Let's get into the real options."

Yue Pingting, "???"

What do you mean?

She looked blank.

Xu Heng smiled and said, "I have already told you very clearly above, the relationship between supply and consumption!"

"Let's look at the multiple-choice questions, but if you provide them, you can get them later, you can get them, you must get them, don't even look at them, just exclude them."

This is Xu Heng's experience!

Yue Pingting was puzzled, "Why?"

Xu Heng, "It can't be counted at all, have you forgotten? You see, it must be less than this value, it can't be calculated."

Yue Pingting slapped her forehead and immediately understood.

"I see!"

For a novice like Yue Pingting, once he gets the hang of it, he will understand it very quickly!

Because she is not impressed by other problem-solving methods!

Xu Heng, "Looking at C, participating in the reaction, how much do you get?"

Yue Pingting blurted out, "0.1mol!"

Xu Heng, "So what?"

Yue Pingting, "So choose C?"

"Yes."

Xu Heng continued, "This is called thickening and thinning. If you provide a number, then you can only calculate the maximum value forever, so the specific number cannot be calculated. Do you understand?"

Yue Pingting nodded, "Yes!"

Xu Heng, "In this case, many calculation problems are not calculation problems!"

Yue Pingting's face was full of question marks, "???"

Calculations, not calculations?

This is chemistry, which requires calculations!Why not a calculation question.

Xu Heng came to pick up a pen and wrote down a question:

12ml of 50mol/L hydrochloric acid reacts with a sufficient amount of MnO2 under heating conditions, and the amount of Cl2 that can be produced is ()

A.0.3mol

B. Less than 0.15mol

C.0.15~0.3mol

D.0.15mol

Xu Heng, "What to choose? Only ten seconds."

Yue Pingting looked at the question in a panic.

"10...9...8...7..."

Yue Pingting, "B! Less than! Less than!"

Xu Heng, "That's right, so do you think this is still a calculation problem?"

Yue Pingting was still in a daze.

At some point, there were already two classmates standing behind them, "It's not a calculation problem!"

Yue Pingting and Xu Heng turned their heads to look.

"???"

"Why are you here?"

The two students smiled, "I was attracted by your lecture! Let's take a look."

"The question you asked is actually the maximum among the four options, but this response cannot be achieved, so the reason is that it is less than, choose B!"

"Less than a certain number is the maximum value!"

"In that case, besides hydrochloric acid, other acids can also be used, right!"

"Next time you encounter such a problem, take a look at the problem and find Xiao Xiao, can't you?"

"Don't say ten seconds, five seconds is enough!"

"Student Xu Heng, you are really amazing!"

A meal of analysis, a meal of praise!

The two students gave thumbs up when they left.

Xu Heng, "Uh..."

Yue Pingting, "Eh..."

baffling!

Yue Pingting curled her lips, "I always feel like I've been robbed!"

Xu Heng waved his hand and looked at Yue Pingting, "Any other questions?"

Yue Pingting shook her head.

She didn't ask Xu Heng any questions until the evening self-study was over.

Instead, answering the dormitory, Yue Pingting and Xu Heng sent messages and asked questions.

Xu Heng, "???"

"You girl, is there something tricky?"

Yue Pingting, "Okay, I admit it, it's my roommates who are asking me questions, but I refused and said no, they said no, ask Xu Heng..."

"It's so hard for me..."

"You say that I am the last one in the class, what do they have to ask!"

Xu Heng smiled, "Try to do it yourself! Treat yourself as a teacher, and you can understand it more thoroughly. If you really don't understand, ask me again."

Yue Pingting, "OK."

Xu Heng quit WeChat and opened the game.

Just went live.

Xiaokang typed, "Brother! You are online!"

Xu Heng typed, "Are you guarding me?"

Xiaokang typed, "Two rounds! I didn't rank myself because I was waiting for you!"