50+50=100

[bharatiyedu]

this is wrong in chemistry wise

 

can anyone explain the reason.

 

we have added 50mL of water and then added 50mL of water to it and the reading is 98 instead of 100. why is that? excludig the erros such as some drops are still in the beaker etc ot in other words think that under perfect conditions.

[FreeThinker]

Did you calibrate the measuring scale?

[Yggdrasil]

When liquids disolve in eachother, their molar volumes can increase or decrease depending on how they interact.

[Darkblade48]

When liquids disolve in eachother, their molar volumes can increase or decrease depending on how they interact.

This would make sense if it was water being mixed with another liquid, but in bharatiyedu's case, it is water being mixed with water. If you measure out 50 mL of water twice, and pour it into another container, barring user error, there should be 100 mL of water.

[jdurg]

I think it's a good lesson about not trusting something just because of what it says it is. There is a very high probability that one of your volume measuring devices is not calibrated properly and is giving you the wrong volume.

 

Another explanation is that you have one volume of water at an elevated temperature and another volume at a depressed temperature. Warm water is less dense than cold water, though I'm not 100% sure that it's a big enough difference to result in 2 mL of difference.

[frostbite]

did you read the upper and lower miniscus? ehhe.. i don't really know what is the answer to your question that but i just gave it a shot. perhaps its because of the temperature. did you take note of the temperature? cause it really affects the readings. STP.

[2810712]

INtelligent point by Yggdrasil abt temp... another pt may be diff conc.s of diff. salts etc. in both , then when they are mixed some temp. changes may occur to change the volume...bad instru u've got to use:embarass:

 

After all science is approximately true, where the approximation is approximately allowable!

[insane_alien]

just tried it with a couple of graduated cylinders both samples at room temperature and it came to 100cm^3 i think you need to regraduate your equipment

[5614]

esp. as it is water + water, there will be no reaction as water doesn't react with itself.

 

Unless it was about 100 degrees and some evaporated or something.

 

Or you didn't completely empty the beaker, or spilled some.

[2810712]

WERE U Using 'really' DISTILLED WATER??? If not, then any reactions are possible...

[Darkblade48]

WERE U Using 'really' DISTILLED WATER??? If not, then any reactions are possible...

Well, even in normal tap water, I can't imagine any reactions that would affect the volume to that extent.

[YT2095]

water does expand 11% upon freezing, so the temp differential that Jdurg pointed out cannot be overlooked as a significant possibility.

the mean average temperature May only occupy a certain volume, whereas seperate, May indicate something greater than.

and don`t forget that the inside of the 2 vessels will remain Wet and thus not All the volume measured will be have been added.

[Chemnut]

Check your sources of error. I would weigh the 50 mL of water, measure the temperature of the water and then lookup the density of water for that temperature and then calculate the volume. D=M/V You should use distilled or deionized water for this measurement. Tap water will be close, but not exact. Are you using glass graduated cylinders or polycarbonate or other? Glass will show a curved meniscus where polycarbonate will be a flat meniscus. Are you reading the bottom of the meniscus or the top? Are you reading the volume at an angle? This would result in paralax causing you to read the incorrect volume. Is your graduated cylinders rated TD (to deliver) or TC (to contain). TC may not be that accurate. If you measured 50 mL of water in a beaker instead of a cylinder, this would be the most likely source of error (a TC container instead of TD container).