To detail the process, thank you 5, to detail the process, thanks

g Amount of hydrogen substance = = mol It takes 2 mol electrons to generate 1 mol of hydrogen, then mol of hydrogen requires mol electrons.

Mol A can donate 1 mol electron, so the valency of A is +2, and Mol Hydrogen requires Mol A, i.e. the amount of G A substance is mol, then the molar mass of A is = 40 g mol, so A is Calcium, Ca

, a is a divalent positive ion.

n hydrogen = m m =

A+2H ions = H2+A2+

a: m n= a is ca

Solution: Let the atom of mol a element lose 1 mol e- to form an ion as an+, then n=2, a + 2h+ = a2+ +h2

mr(a) 2

g g column proportional formula, the solution is mr(a)=40

Therefore, element A is calcium element (Ca).

Answer: A element is calcium element.

So the answer is: calcium.

Angle 1 = 180-115 = 65 degrees.

Angle 2 = 180-45 - Angle 1 = 180-45-65 = 70 degrees.

Angle 3 = 180 - Angle 2 = 180 - 70 = 110 degrees.

The solution consists of 2(ab+bc)=44 and ab=10

The solution yields bc=12

and sabcd=ab*de=bc*df

Know 10 9 = 12 df

The solution yields df = 15 2

If c is hypotenuse, then a 2 + b 2 = c 2, which is inconsistent.

If c is a right-angled edge, then c is less than the hypotenuse, and c 2 is less than the square of the hypotenuse, which is also inconsistent, so it does not exist.

Because the triangle is a right-angled triangle, satisfying the Pythagorean theorem c = a +b does not exist.

Both balls are stationary, which means that the AB rope has no force on the AB2 ball, and the pulling force of the AB rope on B is equal to the gravitational force of B, that is, MG

A ball is affected by gravity mg and oa tension and force f, oab is an equilateral triangle, you can draw a force diagram of a can calculate oa to the ball is equal to 2mg f = 3mg