When does a solar Eclipse happen, and how?

Answers

Answer 1
A solar eclipse occurs when a portion of the Earth is engulfed in a shadow cast by the Moon which fully or partially blocks sunlight. This occurs when the Sun, Moon and Earth are aligned.
Answer 2

Answer:

Solar Eclipse happens when the moon gets between the sun and the earth, the moon gets all the light and blocks the earth from getting sunlight.

Hope this helps ;) ❤❤❤


Related Questions

Enumerate any two differences between simple distillation and fractional distillation.

Answers

Answer:

Explanation:

By simple distillation, we can separate tow miscible liquids having sufficient difference in their boiling points.

By fractional distillation, we can separate the mixture of two or more miscible liquids for which the difference in their boiling point is less than 25k

Simple distillation is done using an air condenser or water condenser.

Fractionating column is fitted in between the distillation flask and the condenser for the process.

Simple distillation eg: mixture of water and acetone

fractional distillation eg: crude oil

hope this helps

plz mark as brainliest!!!!!!

Answer:

Simple Distillation:

1)This method is used for the separation of components of a mixture containing two miscible liquids that boil without decomposition.

2)The components must have sufficient difference in their boiling points.

Fractional Distillation:

1)Fractional distillation process is used to separate a mixture of two or more miscible liquids.

2)If, the components have the difference in boiling points less than 25K .                                                                              

Given the connection between Aw and K (Aw=2k) could you use the ideal gas law and derive the Boltzmann constant. Water freezes at 546.3 Aw and absolute zero is at 0 Aw. (Aw is an arbitrary temperature scale.)

solved, divide boltzmann constant by 2

Answers

Answer:

tails of comets

the ionosphere

a neon sign

Explanation:

what errors can lead to pseudocience?

Answers

Answer:

pseudocience consists of statements, belief or practices that are claimed to be both scientific and factual but are incompatible with the scientific method.

         Errors

use of vague, exaggerated or untestable  claims.over-reliance on confirmation rather than refutation.lack of opennes to testing by other experts.absence of progress.personalization of issues.use of misleading language.

Answer: a prediction or analystment that they though could be a good idea, I said it like this so it would of makes more sense

Which ionic equation for reaction of Magnesium with dilute hydrochloric acid is correct? Mg (s) + 2H+ (aq) â Mg2+ (aq) + H2 (g) Mg (s) + 2HCl (aq) â MgCl2+ (aq) + H2 (g) Mg (s) + 2H+ (aq) â Mg2+ (s) + H2 (g) Mg (s) + H+ (aq) â Mg+ (aq) + H2 (g)

Answers

Answer:

Mg(s) + 2H⁺(aq) ⟶ Mg²⁺(aq) + H₂(g)  

Explanation:

A net ionic equation shows all the ionic substances as ions and shows the correct state of each substance.

B. is wrong. HCl ionizes in aqueous solution into H⁺ and Cl⁻.

C. is wrong. Mg²⁺ is not a solid. It is an aqueous ion.

D. is wrong. The equation needs 2H⁺(aq) to be balanced.

A piece of unknown metal weighs 500 g. When the piece of metal absorbs 6.64 kJ of heat, its temperature increases from 25°C to 78°C. What's the specific heat capacity
of this metal?
A. 13 J/gºC
B. 0.25 J/gºC
C. 25 J/gºC
D.2.5 J/g °C

Answers

6.64×1000÷(78-25)×500=0.25 g/k

Answer:

6.64×1000÷(78-25)×500=0.25 g/k

How many moles of steam, H 2 O react with 1 mol of charcoal, Caccording to the balanced chemical equation? C(s)+H 2 O(g)\ \ CO(g)+H 2 (g)

Answers

Answer:

1 mol

Explanation:

Given:

C(s) + H₂O(g) → CO(g) + H₂(g)

According to the given equation, we can say that 1 mol of steam( H₂O ) reacts with  1 mol of charcoal.

So, 1 mol of steam( H₂O ) is the correct answer.

The answer would be 1 mil

calculate the percentage by mass of chlorine in Cobalt (II) chloride (cocl2)​

Answers

Explanation:

Divide the mass of chlorine by the molar mass of cobalt chloride, then multiply by 100.

Molar Mass of Cobalt Chloride.

Mass of Chlorine in Cobalt Chloride.

Percent Composition of Chlorine.

Divide the mass of chlorine by the molar mass of cobalt chloride, then multiply by 100.
Molar Mass of Cobalt Chloride.
Mass of Chlorine in Cobalt Chloride.
Percent Composition of Chlorine.
Mar 16, 2016

The lock-and-key mechanism refers to
the complementary shapes of an enzyme and a substrate.
the attractive forces between an enzyme and a substrate.
the ability of an enzyme to lower the activation energy of a reaction.
the ability of an enzyme to "unlock" the products of a reaction.

Answers

Answer:

A). The complementary shapes of an enzyme and a substrate.

Explanation:

The Lock-and-key mechanism was proposed by Emil Fischer for the first time and characterized as the metaphor which helps in elucidating the specificity of the enzymatic reactions. In this metaphor, the lock is described as the enzyme while 'key' is characterized as the substrate which the enzyme acts upon. If the key is not appropriately sized, it will not fit into the active site i.e. the keyhole of the lock or enzyme and reaction will not take place. Thus, option A is the correct answer.

the complementary shapes of an enzyme and substrate

A substance X contains 10 gram of calcium carbonate calculate the number of oxide of calcium carbonate present in x​

Answers

Answer:

x contain 9 percent ofcalcium carbonaye

The answer could be x = 10 of calcium

1) what is formed when hydrogen burns ? write the equation for the reaction .
2) why do you think that, when hydrogen burns, the flame Rises quickly ?​

Answers

Answer:

formed by burns rises quickly hydorogen

[tex] H_2+\frac12O_2 \longrightarrow H_2O[/tex]

I don't think I need to name the product.

this reaction is very exothermic. so the gases and the flames are very hot, i.e. very lighter (hot air rises) than the normal air. so it rises quickly

Molar mass is reported on the periodic table in the units

A. kg/m3
B. grams/mole.
C. moles/gram.
D. atoms/gram.

Answers

Answer:

[tex]\boxed{\sf B. \ grams/mole}[/tex]

Explanation:

[tex]\sf The \ molar \ mass \ of \ a \ substance \ is \ the \ mass, \ in \ grams,\ per \ one \ mole.[/tex]

[tex]\displaystyle \sf \frac{grams}{mole}[/tex]

Answer:

B

Explanation:

Grams/mole is correct. Got right on test!

What is the shape of the following molecule? AIF_3

Answers

Answer:

AI + F2 = AIF3

Explanation:

Answer:

The molecular geometry of AlF3 is trigonal planar with a symmetric charge distribution on the central atom. Therefore this molecule is non-polar.

calculate the number of moles equivalent 10.0 gram of aluminium carbonate ​

Answers

[tex] \LARGE{ \boxed{ \red{ \rm{Answer}}}}[/tex]

☃️ Chemical formulae ➝ [tex]\sf{Al_2(CO_3)_3}[/tex]

How to find?

For solving this question, We need to know how to find moles of solution or any substance if a certain weight is given.

[tex] \boxed{ \sf{no. \: of \: moles = \frac{given \: weight}{molecular \: weight} }}[/tex]

Solution:

❍ Molecular weight of [tex]\sf{Al_2(CO_3)_3}[/tex]

= 2 × 27 + 3 × 12 + 9 × 16

= 54 + 36 + 144

= 234

❍ Given weight: 10 g

Then, no. of moles,

⇛ No. of moles = 10 / 234

⇛ No. of moles = 0.0427 moles

⚘ No. of moles of Aluminium carbonate in the given weight = 0.0427 moles.

━━━━━━━━━━━━━━━━━━━━

ok it’s gonna be the c= 12

calculate the number of moles equivalent to 20.0 gram of calcium phosphate ​
please help

Answers

[tex] \LARGE{ \boxed{ \red{ \rm{Answer}}}}[/tex]

☃️ Chemical formulae ➝ [tex]\sf{Ca_3(PO_4)_2}[/tex]

How to find?

For solving this question, We need to know how to find moles of solution or any substance if a certain weight is given.

[tex] \boxed{ \sf{No. \: of \: moles = \frac{Given \: weight}{Molecular \: weight} }}[/tex]

Solution:

Atomic weight of elements:

Ca = 40P = 31O = 16

❍ Molecular weight of [tex]\sf{Ca_3(PO_4)_2}[/tex]

= 3 × 40 + 2 × 31 + 8 × 16

= 120 + 62 + 128

= 310 g/mol

❍ Given weight: 20 g

Then, no. of moles,

⇛ No. of moles = 20 g / 310 g mol‐¹

⇛ No. of moles = 0.0645 moles

⚘ No. of moles of Calcium phospate in the given weight = 0.0645 moles.

━━━━━━━━━━━━━━━━━━━━

Answer:

The answer is 0.08mol

Explanation:

To find the number of moles in calcium phosphate we use the formula

[tex]n \: = \frac{m}{M} [/tex]

where

n is the number of moles

M is the molar mass

m is the mass of the substance

To find the number of moles we must first find the molar mass

Chemical formula for calcium phosphate is

Ca3( PO4)2

Ca = 40 , P = 31 , O = 16

So the Molar mass of calcium phosphate is

M( Ca3( PO4)2 ) = (20×3) + 2( 31 + (16×4)

= 60 + 2( 31 + 64)

= 60 + 2(95)

= 60 + 190

Molar mass of calcium phosphate =

250g/mol

Mass = 20 g

So we have

[tex]n = \frac{20g}{250g/mol} [/tex]

We have the final answer as

n = 0.08 mol

Hope this helps you

Electronic configuration is best described as
a. protons in the nucleus of atom
b. electrons on the outermost orbit
c. attraction of electrons between two atoms
d. arrangement of electrons in an atom​

Answers

Answer:

d

Explanation:

The arrangement of electrons in an atom

Answer:

D. Arrangement of electrons in an atom.

Explanation:

K L M N O P Q

2 8 8 18 18 32 50

The path where electrons revolve is called orbits.

Hope his helps ;) ❤❤❤

I thought in the third shell there are 18 electrons, but why are they gaining only 2 electrons?? Pls tell me... I have exam tomorrow....

Answers

Use this picture to understands.
The picture will help you understand

calculate the number of moles equivalent to 12.7 gram of iodine molecule ​

Answers

[tex] \LARGE{ \boxed{ \purple{ \rm{Answer}}}}[/tex]

☃️ Chemical formulae ➝ [tex]\sf{I_2}[/tex]

How to find?

For solving this question, We need to know how to find moles of solution or any substance if a certain weight is given.

[tex] \boxed{ \sf{No. \: of \: moles = \frac{Given \: weight}{Molecular \: weight} }}[/tex]

Solution:

❍ Molecular weight of [tex]\sf{I_2}[/tex]

= 2 × 126.90

= 253.80

= 254 (approx.)

❍ Given weight: 12.7

Then, no. of moles,

⇛ No. of moles = 12.7 / 254

⇛ No. of moles = 0.05 moles

⚘ No. of moles of Iodine molecule in the given weight = 0.05 moles

━━━━━━━━━━━━━━━━━━━━

Answer:

The answer is 0.05 mol

Explanation:

To find the number of moles (n) we use the formula

[tex]n = \frac{m}{M} [/tex]

Where

n is the number of moles

m is the mass of the substance

M is the molar mass

To find the number of moles we must first find the molar mass

Since iodine is a diatomic molecule

M( I ) = 127 × 2 = 254 g/mol

Mass of iodine = 12.7 g

So the number of moles in 12.7 g of iodine is

[tex]n = \frac{12.7 \: g}{254 \: g/mol} [/tex]

We have the final answer as

n = 0.05 mol

Hope this helps you

A substance X contains 10 gram of calcium carbonate calculate the number of oxide of calcium carbonate present in X ​
please help

Answers

Answer:

I got 0.01 moles, hope this helps!

First you have to calculate the number of moles of caco3 ! Use n=m/M ! YOH will get 0.1 moles ! By using stiochiometry you will get


O3/Caco3 = 48/100 (molar masses ) = x/0.1. ( using moles ) then you will get x = 0.048 moles

remember that it takes 2 electrons to form a bond how many bonds does CIO 3 - have, the chlorate ion

Answers

Answer:

3 bonds

Explanation:

solve this by doing the lewis structure for CIO3

Answer:

3 bonds.

Explanation:

2 double bonds and one single bond.

Which series represents the flow of thermal energy in a home with a refrigeration cooling system?
Inside air coolant in cooling system – outside air
X Fuel
- air inside piston chamber piston movement
Inside air
outside air
Fuel
Inside air​

Answers

Answer

A is the answer

Answer: A








Hope that helps:)

Use the potential energy diagram shown to answer the following: Which letter shows the activation energy(without use of a catalyst)

Answers

Answer:

a

Explanation:

Activation energy is the minimum amount of energy that must be overcome before a reaction will proceed to product.

In the energy diagram, the thick line represent the uncatalyzed path while the broken line line indicates the catalyzed path.

In the diagram above, the letter between the reactant and the Peak of the diagram gives the activation energy. This letter is a.

Therefore, the activation energy for the uncatalyzed reaction is 'a'.

the answer to this question is a because yu use the diagram

Ice sinks in methanol, but floats on water. From this we can conclude: A The density of ice in methanol must be different from that in water. B The density of water must be less than the density of methanol. C The density of ice must be greater than the density of water. D The density of methanol must be less than the density of water.

Answers

Answer:

A

Explanation:

Density: water>ice>methanol

Ice is lighter than methanol hence it is able to float on it. However, ice is denser than water hence it sinks.

Answer:

The answer is A.

Explanation:

The density of ice in methanol must be different from that in water.

Examine the assumption. Assumption: The Earth is flat. Which statements accurately describe how the assumption affects scientific thinking? (Select all that apply. People think the Earth is flat, so they think that the Earth does tilt on its axis while revolving around the Sun. People think the Earth is flat, so they think that it is only safe to travel certain distances from a given location. People think the Earth is flat, so they think that when the Sun sets, it goes underneath the Earth. People think the Earth is flat, so they think that when traveling in a straight line, there is no end.

Answers

Answer:

The statements that accurately  describe how the assumptions affects scientific thinking are;

People think that the Earth is flat, so they think that it is only safe to travel certain distances from a given location.

People think that the Earth is flat, so think that when the Sun sets, it does underneath the Earth

Explanation:

The proof that the Earth is round was made by the Greek philosopher, Aristotle, over 2,000 years ago, by observation of the change in the constellation of the stars as a person changes his position North or South

The initial belief was that the Earth is flat disc surrounded by water, while the it was believed that the shape of the Earth was that of a square with four mountains at the vertices that support the sky from falling.

the statements are the answer are the problem to

Study this chemical reaction:
Ti+02 - TiO2
Then, write balanced half-reactions describing the oxidation and reduction that happen in this reaction.
oxidation:

reduction:​

Answers

Answer:

oxidation:Ti to Ti           Reduction:O2 toO2

Explanation:

oxidation loses electron while Reduction gains electron

-8 because you need to subtract

Suppose 300 mL of 0.50 M lithium bromide solution and 300 mL of 0.70 M rubidium bromide solution are combined. What is the concentration of the bromide ion in the resulting solution?

Answers

Answer:

0.60 mol·L⁻¹  

Explanation:

Data:  

LiBr: c = 0.50 mol/L; V =300 mL

RbBr: c = 0.70 mol/L; V =300 mL

1. Calculate the moles of Br⁻ in each solution

(a) LiBr

[tex]\text{Moles} = \text{0.300 L} \times \dfrac{\text{0.50 mol}}{\text{1 L}} = \text{ 0.150 mol}[/tex]

(b) RbBr

[tex]\text{Moles} = \text{0.300 L} \times \dfrac{\text{0.70 mol}}{\text{1 L}} = \text{ 0.210 mol}[/tex]

2. Calculate the molar concentration of Br⁻

(a) Moles of Br⁻

n = 0.150 mol  + 0.210 mol = 0.360 mol

(b) Volume of solution

V = 300 mL + 300 mL = 600 mL = 0.600 L

(c) Molar concentration

[tex]c = \dfrac{\text{moles}}{\text{litres}} = \dfrac{\text{0.360 mol}}{\text{0.600 L}} = \textbf{0.60 mol/L}[/tex]

 

The concentration of Br ions in the resulting solution of LiBr and RbBr has been 0.6 M.

The addition of LiBr and RbBr has been dissociated into the equal moles of Li, Rb, and Br.

[tex]\rm LiBr\;\rightarrow\;Li^+\;+\;Br^-[/tex]

[tex]\rm RbBr\;\rightarrow\;Rb^+\;+\;Br^-[/tex]

Thus 1 mole of LiBr = 1 mole Br

1 mole RbBr = 1 mole Br.

The moles of LiBr in 0.5 M solution:

Molarity = [tex]\rm moles\;\times\;\dfrac{1000}{volume\;(ml)}[/tex]

0.5 = [tex]\rm moles\;\times\;\dfrac{1000}{300\;ml}[/tex]

Moles of LiBr = 0.15 mol

The moles of Br from LiBr = 0.15 mol.

The moles of RbBr in 0.7 M solution:

Molarity = [tex]\rm moles\;\times\;\dfrac{1000}{volume\;(ml)}[/tex]

0.7 = [tex]\rm moles\;\times\;\dfrac{1000}{300\;ml}[/tex]

Moles of RbBr = 0.21 mol

The moles of Br from RbBr = 0.21 mol.

The total moles of Br ions from LiBr and RbBr has been :

= 0.15 + 0.21

= 0.36 mol.

The total volume of the solution will be:

= 300 + 300 ml

= 600 ml.

The concentration of the Br ion has been:

Molarity = [tex]\rm moles\;\times\;\dfrac{1000}{volume\;(ml)}[/tex]

Molarity of Br ions =  [tex]\rm 0.36\;\times\;\dfrac{1000}{600\;ml}[/tex]

Molarity of Br ions = 0.6 M.

The concentration of Br ions in the resulting solution of LiBr and RbBr has been 0.6 M.

For more information about the concentration of the sample, refer to the link:

https://brainly.com/question/11804141

How many lead (Pb) atoms will be generated when 5.38 moles of ammonia react according to the following equation: 3PbO+2NH3→3Pb+N2+3H2O?
A) 1.62 × 10^24
B) 4.86 × 10^23
C) 2.43 × 10^24
D) 4.86 × 10^24

Answers

Answer:D. Is the correct answer

Explanation:

Following are the calculation of the lead (Pb) atoms:

Balanced reaction:  

[tex]\bold{3PbO+2NH_3\longrightarrow 3Pb+N2+3H2O}\\\\[/tex]

[tex]\bold{mol\ NH_3 \longrightarrow mol \ Pb \longrightarrow atoms \ Pb}[/tex]

Calculating the number of atoms in Pb that will be generated:

[tex]=5.38 \ mol \ NH_3 \times \frac{3\ mol\ Pb}{2 \ mol NH_3} \times \frac{6.022 \times 10^{23} \times pb}{1 \ mol \ pb}\\\\ = 4.86 \times 10^{24} \ atoms\ in \ Pb\\\\= 4.86 \times 10^{24} \ atoms \\[/tex]

Therefore, the answer is "Option D"

Learn more:

brainly.com/question/21092165

Glucose has formula C6 H12 O6.
Calculate the number of Hydrogen atoms present in 18 g of glucose

please help​​

Answers

The answer is 6.0•1022
I’m sorry I’m working on this one too

A subtance X contains 10 gram of calcium carbonate calculate the number of oxygen atom present in 10 gram of calcium carbonate ​

Answers

[tex] \LARGE{ \boxed{ \rm{ \purple{Required \: answer}}}}[/tex]

☃️ Chemical formulae ➝ [tex]\sf{CaCO_3}[/tex]

How to find?

For solving this question, We need to know how to find moles of solution or any substance if a certain weight is given.

[tex] \boxed{ \sf{No. \: of \: moles = \frac{given \: weight}{molecular \: weight} }}[/tex]

And, Then we need to find the number of molecules which can be found by:

[tex] \large{ \boxed{ \sf{no. \: of \: molecules = N_A \times no. \: of \: moles}}}[/tex]

Here, Na = Avagadro Number (6.022 × 10²³)

☀️ As it is a compund, We considered molecules. Then, we can predict the no. of atoms of elements in one molecule of compound and get the answer.

Solution:

Atomic weight of elements:

Ca = 40C = 12O = 16

❍ Molecular weight of [tex]\sf{CaCO_3}[/tex]

= 40 + 12 + 3 × 16

= 52 + 48

= 100 g/mol

❍ Given weight: 10 g

Then, no. of moles,

⇛ No. of moles = 10 g / 100 g mol‐¹

⇛ No. of moles = 0.1 moles

☄ No. of moles of Calcium carbonate in the given weight = 0.1 moles

Finding no. of molecules,

⇛ No. of molecules of CaCO3 = 0.1 × 6.022 × 10²³

⇛ No. of molecules of CaCO3 = 6.022 × 10²²

Now,

1 molecule of [tex]\sf{CaCO_3}[/tex] = 3 atoms of Oxygen.

Then, 6.022 × 10²² molecules will have,

= 3 × 6.022 × 10²² atoms of oxygen

= 18.022 × 10²² atoms of oxygen

In more scientific form,

= 1.8022 × 10²³ atoms of oxygen

☄ Hence, Final answer - 1.8022 × 10²³ atoms

━━━━━━━━━━━━━━━━━━━━

CaCo3 is the answer to this

Magnesium nitrate, magnesium hydroxide and magnesium carbonate all decompose when heated.
Which statement about these decomposition reactions is correct?
A. Magnesium carbonate decomposes to release carbon dioxide and oxygen
B. Magnesium hydroxide decomposes to release hydrogen and oxygen
C. Magnesium hydroxide decomposes to release water vapour
D. Magnesium nitrate decomposes to release oxygen only​

Answers

Answer:

C

Explanation:

The reactions:

[tex] \mathrm{Mg(NO_3)_2 \longrightarrow MgO+ 2NO_2 +O_2}\\

\mathrm{Mg(OH)_2 \longrightarrow MgO + H_2O}\\

\mathrm{MgCO_3 \longrightarrow MgO +CO_2}[/tex]

If you are trying to measure an
electric current and need to describe the quantity
and units, how will you describe the units?

Answers

Answer:

Usually you have V, for voltage, Ohms for resistance, and Coulombs for charge.

Explanation:

See the image attached :)

You would use v for Volta
Other Questions
What would happen to the rate of a reaction with rate law rate = k [NO]2[Hz] ifthe concentration of NO were doubled? please help!A. dark brown sea lions absorb too much heat from the sun during the dayB. dark brown sea lions blend in with the color of rocks and escape predatorsC. light brown sea lions fish prey are attracted to the light color of their fur coatD. light brown sea lions are able to compete with other organisms for resources At what phase should security planning begin in a conceptual and proposed "from the start" international acquisition program? Simple math! What is the issue with my work? I got it wrong. Find four consecutive integers such that twice the 3rd number decreased by the second numberis 8 Which of the following uses hyphens correctly?O A. The movie was a re-made back in the 1980's.B. We went to watch the actor's re-creation of the Civil War.OC. The next project for the house is to re-do the kitchen.OD. The queen was dressed in a re-gal purple gown. If forces acting on an object are unbalanced, the object could experience a change in ________. If pattern of inheritance is complete dominance what would you expect when a red and yellow fish were crossed There are 9 students at the math club picnic. If 3 students are drinking punch and 6 are drinking lemonade, what fraction are drinking lemonade Which of the following choices evaluates (-x)^2 when x=-1Answers:1)12)-23)-1 Strikes are much more disruptive in pro sports than in mainstream business because A. players have unique talents and cannot be replaced with temporary replacement workers. B. professional athletes' salaries are so much higher than the average worker. C. sports are seasonal, thus have less time to realize revenue. D. All of these are correct. What is nine thousandths as a decimal TB MC Qu. 8-187 The Charade Corporation is preparing its ... The Charade Corporation is preparing its Manufacturing Overhead budget for the fourth quarter of the year. The budgeted variable manufacturing overhead is $5 per direct labor-hour; the budgeted fixed manufacturing overhead is $95,000 per month, of which $17,000 is factory depreciation. If the budgeted direct labor time for November is 9,000 hours, then the total budgeted manufacturing overhead for November is: The expression 6(x 5) means the . If x = 7, the value of the expression is WILL GIVE BRAINLY!!!!describe how the line of best fit and the correlation coefficient can be used to determine the correlation between two variables on a graph If SSR is 2592 and SSE is 608, then A. the standard error would be large. B. the coefficient of determination is .23. C. the slope is likely to be insignificant. D. the coefficient of determination is .81. 1) What is India size and location ? An electron and a proton are 6.5x10 ^ -11 m apart, find the magnitude of the electric and gravitational force between the two particles Study the table. Which best describes the function represented by the data in the table? What is the reason: if a+c=b+c then a=b