Answer: 1. halve
2. halve
3. double
Explanation:
The relationship between wavelength and energy of the wave follows the equation:

E= energy
= wavelength of the wave
h = Planck's constant
c = speed of light
Thus as wavelength and energy have inverse realation, when wavelength will halve , energy will double.
2. The between wavenumber and energy of the wave follows the equation:

E= energy

= wavenumber of the wave
h = Planck's constant
c = speed of light
Thus as wavenumber and energy have direct relation, when wavenumber will halve , energy will be halved.
3. The relationship between energy and frequency of the wave follows the equation:

where
E = energy
h = Planck's constant
= frequency of the wave
Thus as frequency and energy have direct realation, when frequency will double , energy will double.
Answer:
no.it is false.some are useful.like mixture of h2 and O 2 to form water.
Chemical reaction: Ba(NO₃)₂ + H₂SO₄ → BaSO₄ + 2HNO₃.
V(H₂SO₄) = 250 mL ÷ 1000 mL/L = 0,25 L.
m(BaSO₄) = 0,55 g.
n(BaSO₄) = m(BaSO₄) ÷ M(BaSO₄).
n(BaSO₄) = 0,55 g ÷ 233,38 g/mol.
n(BaSO₄) = 0,00235 mol.
From chemical reaction: n(BaSO₄) : n(Ba(NO₃)₂) = 1 : 1.
n(Ba(NO₃)₂) = 0,00235 mol.
c(Ba(NO₃)₂) = n(Ba(NO₃)₂) ÷ V.
c(Ba(NO₃)₂) = 0,00235 mol ÷ 0,25 L.
c(Ba(NO₃)₂) = 0,0095 mol/L.