Answer is (3) both mass number and atomic number.
The notation is ₅₅¹³⁷Cs. The Cs represents the chemical symbol of Caesium element. The subscript number at the left hand side of the symbol indicates the atomic number. Hence, atomic number of Cs is 55. The superscript number at the left hand side of the symbol shows the mass number. Hence, the mass number of the Cs is 137.
Answer:
A
Explanation:
Hot air is less dense therefore it rises. Cold air is more closely packed therefore it is more dense. Less dense things rise while more dense things sink.
A substance that readily burns
when it comes into contact with a flame has the chemical property of
reactivity. The answer is letter C. Reactivity is a chemical property of a
substance. According to EPA regulations, it is normally unstable and readily undergoes
violent change without detonating. it can explode or violently react when
exposed to water, when heated, or under STP.
Answer:
D
Explanation:
Recall that entropy measures the number of microstates in a substance, which is highest in gases, followed by liquids and solids. Hence, entropy increases if the products have more gaseous molecules than the reactants.
- In reaction one, chlorine gas is converted into solid NaCl, so entropy decreaes.
- In reaction two, four moles of gas are converted into two moles of gas, so entropy decreases.
- In reaction three, ice is melted to form water, which has higher entropy. Thus, entropy increases.
- In reaction four, a liquid is freezed into its solid phase, leading to a decrease in entropy.
- In reaction five, oxygen gas is converted into solid MgO, so entropy decreases.
In conclusion, the answer is D.
Reaction of methyl amine with HCl (H+) is:
CH3NH2 + H⁺ ↔ CH3NH3⁺
At equivalence point:
moles of CH3NH2 = moles of HCl
moles of CH3NH2 = 0.350 * 0.125 = 0.0438 moles = moles of HCl
Volume of HCl = 0.0438 / 0.250 = 0.1752 L
Therefore, total volume at eq point = 0.350 + 0.1752 = 0.5252 L
Now, at equivalence point there is 0.0438 moles of CH3NH3+. The new equilibrium is :-
CH3NH3+ ↔ CH3NH2 + H+
where the concentration of CH3NH3+ = 0.0438/0.5252 = 0.083 M
Ka = [CH3NH2][H+]/[CH3NH3+]
Kw/Kb = x²/0.083-x
10⁻¹⁴/4.4*10⁻⁴ = x²/0.083-x
therefore x = [H+] = 1.37*10⁻⁶M
pH = -log[H+] = -log[1.37*10⁻⁶] = 5.86
