Answer: m= 0.69 m or mol/kg
Explanation: Molality is expressed as moles per unit kilograms of solvent or m= n / kg
First convert 25.0 g NaCl to moles
25.0 g NaCl x 1 mole NaCl / 58 g NaCl
= 0.43 moles NaCl
Next convert 625 g H2O to kilograms
625 g H2O x 1 kg / 1000 g H2O
= 0.625 kg H2O
Substitute the values in the formula
m = n / kg
= 0.43 mole NaCl / 0.625 kg
= 0.69 m or mole / kg
Answer:
The correct answer is <em>D) Niels Bohr</em>
Explanation:
Bohr proposed a new atomic model, whereby he explains that electrons rotate around the nucleus at well-defined levels, describing circular orbits. Each orbit was called the energy level (it is called the main quantum number n, going from numbers 1 to 7). To make his model, Bohr studied the Hydrogen atom (it has a proton in its nucleus and an electron rotating around it).
Mr: 207.2
m=n×Mr= 6.53×207.2= 1353.02g
Answer:
1s2 2s2 2p6
Explanation:
The nitride ion(N^3-) is formed when nitrogen gains three electrons. Nitrogen possesses seven electrons in its orbitals and ordinarily has the electronic configuration; 1s2 2s2 2p3. However,being in group 15, nitrogen can accept three electrons to form the nitride ion and complete its octet of electrons. When this happens, three electrons are added to the nitrogen atom and the electronic configuration is now the same as that of Neon, its closest noble gas which is 1s2 2s2 2p6. Hence the answer given above.
Elements can accept or donate electrons in order to complete their octet structure in accordance to the octet rule which states that atoms and ions must possess eight electrons in their outermost shell in order to attain chemical stability. The reason for ion formation and chemical reaction is in order for species to attain the octet structure.
