Why do small beakers first weigh the mass roughly on a bench scale and then weigh it accurately on a

The reason why small beakers first roughly weigh mass on a bench scale and then accurately weigh on an analytical balance is mainly to improve weighing accuracy and efficiency.

Specifically, bench scales have low accuracy, and they can be used to roughly measure the mass of small beakers to quickly obtain an approximate result, which is convenient for further estimation and operation. However, due to the low accuracy of the bench scale, directly using it for accurate weighing may produce large errors and affect the accuracy of experimental results.

Analytical balances, on the other hand, are so precise to five or more decimal places that they can be used for accurate mass weighing of small beakers. If an analytical balance is used directly without a rough estimate, it may be necessary to adjust a very large range, such as from 0 to the actual mass of the beaker, which can be time-consuming and difficult to control. By first using a bench scale to roughly measure the mass of a small beaker, the range that needs to be adjusted can be narrowed down to a smaller range, such as from to.

This allows for a much smaller range of adjustments, such as from to, when using an analytical balance for accurate weighing.

Therefore, the method of coarsely weighing the mass on the bench scale and then accurately weighing the beaker on the analytical balance can improve the accuracy of the weighing and also improve the work efficiency.

If the beaker mass is a decimal, and if an analytical balance with an accuracy is used at the outset, then the range of adjustments required is particularly large (0 to . However, if the first digits are determined with a balance with slightly lower accuracy, e.g. between to, then when measured with an analytical balance, the range to be adjusted is very small (to). Just as an example, don't be more realistic about the specific data

It's chemistry.

cao+h2so4=caso4+h2o

fe+h2so4=feso4+h2↑

It can be seen that when iron reacts with dilute sulfuric acid, gas is generated, and the mass of the left disk decreases, while the mass of calcium oxide does not decrease after the reaction with dilute sulfuric acid, so the mass of the right disk does not change.

At the beginning, the left disc increased by 8 grams, the right disc increased grams, and then balanced, and we know that the quality of the right disc of the file hole has changed, so the mass of the left disc decreases = the gram line is greatly withered.

It can be seen from the reaction formula that 1 mole of iron reacts, releases 1 mole of hydrogen, reduces the mass to 2 grams, and now reduces the grams, so the iron should be moles, and the mass of iron = 56 * grams.

The accuracy of the tray balance is so weigh a small beaker.

The quality of the only hail refers to the sail, and the accurate scalar readings are; Therefore, the answer is: c

Answer: B Tray balances can be used to roughly weigh the mass of an object, generally to g

Dilute sulfuric acid of equal mass and equal mass fraction is added to the same mass of magnesium powder and zinc powder respectively, and if neither of them reacts, the balance is still balanced. react but the acid is insufficient (the metal is left or the zinc is just finished), and the balance is still balanced.

In other cases, the balance is biased towards the side of the powder, because the powder produces more hydrogen than the powder (i.e. more mass is lost in the beaker), so it is absolutely impossible for the balance to be biased on the side of the powder.

c From the question, it can be seen that the mass of magnesium powder may be greater than or equal to the mass of zinc powder, and according to the activity of the metal, magnesium reacts faster than zinc, so it is impossible to appear c

First, place the balance on a horizontal table, reset the yard to zero, and adjust the balance nut to balance the balance in a horizontal position.

Then, place the beaker on the left disc of the scale, add weights to the right disc or move the yard to the right until the balance is balanced for the second time, at which point the total mass of the weights and yards in the right disc is the mass of the empty beaker.

Then, in a few steps, add 200g of weights directly to the right plate and slowly add water to the beaker until the balance is balanced for the third time.

The mass of water in the beaker is 200g.

What does it mean to be accurate? It's a bit too general.

Conservation of mass 2Fe+2HCl=FeCl2+H2

y x gets x= is hydrogen y=

Because hydrochloric acid is a sufficient amount of divalent iron ions, hydrochloric acid will continue to oxidize to iron ions:

2fecl2+2hcl=2fecl3+h2

z gets z= so the mass of hydrogen produced is the actual weight added in the small beaker on the left.

The mass of calcium carbonate added on the right minus the amount of carbon dioxide produced should also be equal to so.

caco3+2hcl=cacl2+h2o+co2

a a is approximately equal to.

I think the steps are right Maybe there are still people who will be able to help you get here Let's study together The landlord is researching and researching Option D is the closest It's best to ask the teacher hehe

nfe=

nh2=

Therefore, the remaining mass in the beaker at this time is the mass of the added iron - the mass of the hydrogen that runs away = and the other side is set to NCACO3=xmol, then the produced NCO2=XMOL is also added - run away: (100-44)x=x=

mcaco3=100x=

Because Fe+HCl produces hydrogen, calcium carbonate and hydrochloric acid produce carbon dioxide, because hydrochloric acid is sufficient, FE and calcium carbonate all react.

Iron produces hydrogen, which means that the actual weight of the left tray is (M beaker + M tray + M hydrochloric acid + right tray weight (M beaker + M tray + M hydrochloric acid + MCACO3-MCO2) because M beaker + M tray + M hydrochloric acid + M tray + M tray + M hydrochloric acid + M tray + MCACO3-MCO2

So mcaco3-mco2=

According to m=n·m

Get 100 ncaco3-44 nco2 = because ncaco3 = nco2

So ncaco3=

So mcaco3=(

So choose d to understand it, I hope it will help the landlord.

Fe+2HCl==FeCl2+H2 Suppose 1molFe is added, 1molH2 is generated, and the mass is increased by 56-2=54g

So the actual increase in mass is.

CaCO3+2HCl==CaCl2+H2O+CO2 In the same way, assuming that m grams are added, m*56 100 is actually increased

So to balance, the left side actually increases, and the right side has to increase (54 56) (56 100).

(Conservation of mass, in addition to the formation of gas runs away, the amount of matter added, the mass increases) is detailed enough

A. The tray balance is used to roughly weigh the quality of the drug, which can be accurate, so the tray balance is used to weigh NaCl, so A is wrong; B. The 10ml graduated cylinder can be accurate, so the hydrochloric acid can be measured with a 10ml graduated cylinder, so B is correct; c. The beaker is used to roughly measure the volume of the liquid, and 15ml of solution can be measured from a 50ml beaker, so c is wrong; D. The volumetric flask is an instrument used to accurately prepare the quantity and concentration solution of a certain substance, and the concentration value should be kept to 2 decimal places, so the 100ml volumetric flask is used to prepare 100ml mol L-1 NaCl solution, so D is wrong so choose B