题目

最好难一些.

提问时间：2021-03-25

答案

Solid NH4Cl is added to the preceding equilibrium.What will happen to the forward and reverse rates?(氯化铵分解成氨气和氯化氢)
Forward Rate Reverse Rate
A.increases increases
B.no change no change
C.increases decreases
D.decreases increases
选A
1:Explain how a gas exerts pressure on a surface?
please answer in english.
2:Give an example of something that might use this property that liquid is dificult to be simpress.
1st.A constant beating on the surface of a container by moleculars shows the macroscopical pressure.Though the kenitic energy and the momentum of a single molecular are tenuity,vast amount of moleculars perform a macroscopical property which can hardly be ignored.
2nd.i don`t quite understant the word 'simpress'.
some gas is collected over water at 20.0℃.the level of water inside and outside the gas-collection bottle are the same .the partral pressure of hydrogen is 742.5 torr
what is the barometric pressure at the time the gas is collceted?
答案是760.0 torr
the water vapor is saturated in the gas-collection bottle.at 20.0℃,the saturated vapor pressure of water is 2309 Pa,that is 17.5 torr.thus,the barometric pressure,equal to the total pressure in the bottle,is (742.5+17.5=)760.0 torr.
1：How do homogeneous mixtures differ from heterogeneous mixtures?where does the compound table salt(NaCl)fit into this description?
2：Are atoms positive,negative,or neutral in charge?Explain
3：If an element's atomic mass and atomic number are known,what else can be determined?Give an example to demonstrate your understanding.
1.A homogeneous mixture is a mixture in which all particles are uniformly distributed.heterogeneous mixtures is a mixture in which all particles are not uniformly distributed.NaCl fits into the homogeneous group because on the microscopic level (i.e.:looking at salt at the crystal structure level),we see that the arrange is uniform,that is,it repeats in a pattern in an infinite direction.At the macroscopic level (i.e.:using the naked eye),just having a bowl of salt on the table,you can see that the salt is the same throughout the bowl,that is,it is uniform.
2.atoms has neutral charge because atoms has the same amount of protons (positive charge) and electrons (negative charge).The positive and negative charges therefore cancel each other out perfectly.
3.Numbers of neutrons.because the Atomic mass is determined by the Atomic number plus the number of neutrons.
A= Z + N,where N is the number of neutrons
where A is the Atomic Mass
where Z is the Atomic number (number of proton)
for example-hydrogen have 1 proton and its atomic number is also 1
number of neutrons+number of protons=atomic mass
for example-hydrogen have 1 proton and 1 electron
so atomic mass of hydrogen is 1+1=2