Caffeine has the following percent composition: carbon 49.48%, hydrogen 5.19%, oxygen 16.48% and nitrogen 28.85%. Its molecular weight is 194.19 g/mol.
Which of these is an isoelectronic series? 1) na+, k+, rb+, cs+ 2) k+, ca2+, or, s2– 3) na+, mg2+, s2–, cl– 4) li, be, b, c 5) n
ss7ja [257]
An isoelectronic series is where all of the ions listed have the same number of electrons in their atoms. When an atom has net charge of zero or neutral, it has equal number of protons and electrons. Hence, it means that the atomic number = no. of protons = no. of electrons. If these atoms become ions, they gain a net charge of + or -. Positive ions are cations. This means that they readily GIVE UP electrons, whereas negative ions (anions) readily ACCEPT electrons. So, to know which of these are isoelectronic, let's establish first the number of electron in a neutral atom from the periodic table:
Na=11; K=19; Rb=37; Cs = 55; Ca=20; S=16; Mg=12; Li=3; Be=4; B=5; C=6
A. Na⁺: 11-1 = 10 electrons
K⁺: 19 - 1 = 18 electrons
Rb⁺: 37-1 = 36 electrons
B. K⁺: 19 - 1 = 18 electrons
Ca²⁺: 20 - 2 = 18 electrons
S²⁻: 16 +2 = 18 electrons
C. Na⁺: 11-1 = 10 electrons
Mg²⁺: 12 - 2 = 10 electrons
S²⁻: 16 +2 = 18 electrons
D. Li=3 electrons
Be=4 electrons
B=5 electrons
C=6 electrons
The answer is letter B.
First of all the ethylamine is base so will be react with water to take the proton from the water (H⁺) , because water is amphoteric will react with bases as acid and acids as a base, so the water in this case will react as an acid and will gives the proton to the base.
In the picture you may see the chemical equation and the structure of the products.
Answer:
Fe(s) → Fe²⁺(aq) + 2e⁻ OXIDATION
Mg²⁺(aq) + 2e⁻ → Mg(s) REDUCTION
Explanation:
The redox reaction is: MgCl₂(aq) + Fe(s) → FeCl₂(aq) + Mg(s)
We need to know that elements in ground state have 0 as the oxidation state.
Iron in the reactants, and Mg in the products
In the magnessium chloride, the Mg acts with+2, so the oxidation state has decreased → REDUCTION
In the iron(II) chloride, the Fe acts with +2, so the oxidation statehas increased → OXIDATION
The half reactions are:
Fe(s) → Fe²⁺(aq) + 2e⁻ OXIDATION
Mg²⁺(aq) + 2e⁻ → Mg(s) REDUCTION
Explanation:
The solution of the lactic acd and sodium lactate is referred to as a buffer solution.
A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. In this case, the weak acid is the lactic acid and the conjugate base is the sodium lactate.
Buffer solutions are generally known to resist change in pH values.
When a strong base (in this case, NaOH) is added to the buffer, the lactic acid will give up its H+ in order to transform the base (OH-) into water (H2O) and the conjugate base, so we have:
HA + OH- → A- + H2O.
Since the added OH- is consumed by this reaction, the pH will change only slightly.
The NaOH reacts with the weak acid present in the buffer sollution.
