To double the average kinetic energy of helium atoms in a balloon at 27 °C, the temperature of the gas must be

54°C

Explanation:

Hello,

To find the temperature of the gas, we would need a relationship between kinetic energy and temperature.

K.E = 3/2RT/Na

Where K.E = kinetic energy

R = ideal gas constant

T = temperature of the ideal gas

Na = Avogadro's number

2K.E₁ = K.E₂ (required)

Since both constant (R and Na) are equal,

K.E = T (direct proportionality)

But T = 27°C

T2 = 2 × 27 = 54°C

To double the kinetic energy of a helium gas at 27°C the temperature of the gas should be increased to 54°C

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.