There are 18groups in modern periodic table.
- The modern periodic table is discovered by famous scientist Henry Mosley in 1914.
- The modern periodic table is also called long term periodic table.
- It has 7periods and 18groups.
Answer:
1.23 M
Explanation:
Molarity of a substance , is the number of moles present in a liter of solution .
M = n / V
M = molarity
V = volume of solution in liter ,
n = moles of solute ,
Moles is denoted by given mass divided by the molecular mass ,
Hence ,
n = w / m
n = moles ,
w = given mass ,
m = molecular mass .
From the question ,
w = given mass of NaCl = 7.2 g
As we know , the molecular mass of NaCl = 58.5 g/mol
Moles is calculated as -
n = w / m = 7.2 g / 58.5 g/mol = 0.123 mol
Molarity is calculated as -
V = 100ml = 0.1 L (since , 1 ml = 1/1000L )
M = n / V = 0.123 mol / 0.1 L = 1.23 M
Answer:
For federal offices (President, Vice President, and United States Congress), Election Day occurs only in even-numbered years. Presidential elections are held every four years, in years divisible by four, in which electors for President and Vice President are chosen according to the method determined by each state.
Explanation:
Answer is: pH value of weak acid is 3.15.<span>
Chemical reaction: HA(aq) </span>⇄ A⁻(aq) + H⁺<span>(aq).
c(weak acid) = 0,5 M.
Ka(weak acid) = 1.0</span>·10⁻⁶.
[A⁻] = [H⁺] = x.
[HA] = 0.5 M - x.
Ka = [A⁻]·[H⁺] / [HA].<span>
</span>1.0·10⁻⁶ = x² / (0,5 M - x).
Solve quadratic equation: x = [H⁺] = 0.0007 M.
pH = -log[H⁺].
pH = -log(0.0007 M).
pH = 3.15.