Al +3CuCl--->AlCl3+3Cu , its balanced equation
Acid is anything which will give H+ to other species.
Have a look at the equations given.
In A) HCl changes to Cl- by giving its H+ to H2O. So HCl is an acid.
In B) HCO3- changes to H2CO3^2- by accepting H+. It did Not give its H+ rather it takes from other species. So it is not an acid at all.
In C) H2O is just breaking to H+ and OH-. It is not giving H+ to other species. So it is also not an acid in this reaction.
In D) HCOOH is giving its H+ to H2O. So it is also an acid.
So out of all reactions with water. The only two species are acting as acid with water namely HCl and HCOOH.
Out of these two HCl is very strong acid but HCOOH is a weak acid.
So the answer is D
They are identical to the nucleus of the helium-4 atom. So the answer is helium atoms.
Hope this helps! :)
Answer:
Absolute error 
% Error 
5
Explanation:
The absolute error is the the difference in the measured value and the actual value of a quantity.
Here the actual value is 
grams
The measured value is 
grams
Absolute error
Percent error
Where AE stands for absolute error and AV stands for absolute value.
%
