When acids react with bases they produce salt and water such as:
HCl + NaOH → NaCl + H₂O
According to strength of acid and base, we have 4 types of salts:
salt of strong acid and strong base like: NaCl
salt of weak acid and strong base like: CH₃COONa
salt of strong acid and weak base like: NH₄Cl
salt of weak acid and weak base like: CH₃COONH₄
Electronegativity is the strength an atom has to attract a bonding pair of electrons to itself. When a chlorine atom covalently bonds to another chlorine atom, the shared electron pair is shared equally. The electron density that comprises the covalent bond is located halfway between the two atoms.
But what happens when the two atoms involved in a bond aren’t the same? The two positively charged nuclei have different attractive forces; they “pull” on the electron pair to different degrees. The end result is that the electron pair is shifted toward one atom.
ATTRACTING ELECTRONS: ELECTRONEGATIVITIES
The larger the value of the electronegativity, the greater the atom’s strength to attract a bonding pair of electrons. The following figure shows the electronegativity values of the various elements below each element symbol on the periodic table. With a few exceptions, the electronegativities increase, from left to right, in a period, and decrease, from top to bottom, in a family.
Electronegativities give information about what will happen to the bonding pair of electrons when two atoms bond. A bond in which the electron pair is equally shared is called a nonpolar covalent bond. You have a nonpolar covalent bond anytime the two atoms involved in the bond are the same or anytime the difference in the electronegativities of the atoms involved in the bond is very small.

Now consider hydrogen chloride (HCl). Hydrogen has an electronegativity of 2.1, and chlorine has an electronegativity of 3.0. The electron pair that is bonding HCl together shifts toward the chlorine atom because it has a larger electronegativity value.
A bond in which the electron pair is shifted toward one atom is called a polar covalent bond. The atom that more strongly attracts the bonding electron pair is slightly more negative, while the other atom is slightly more positive. The larger the difference in the electronegativities, the more negative and positive the atoms become.
Now look at a case in which the two atoms have extremely different electronegativities — sodium chloride (NaCl). Sodium chloride is ionically bonded. An electron has transferred from sodium to chlorine. Sodium has an electronegativity of 1.0, and chlorine has an electronegativity of 3.0.
That’s an electronegativity difference of 2.0 (3.0 – 1.0), making the bond between the two atoms very, very polar. In fact, the electronegativity difference provides another way of predicting the kind of bond that will form between two elements, as indicated in the following table.
Electronegativity DifferenceType of Bond Formed0.0 to 0.2nonpolar covalent0.3 to 1.4polar covalent> 1.5ionic
The presence of a polar covalent bond in a molecule can
Divide
Answer: 670K
Explanation:
Given that,
Original volume of gas V1 = 1.22 L
Original temperature T1 = 286 K
New volume V2 = 2.86 L
New temperature T2 = ?
Since volume and temperature are involved while pressure is constant, apply the formula for Charles law
V1/T1 = V2/T2
1.22 L/286 K = 2.86 L/ T2
Cross multiply
1.22 L x T2 = 286 K x 2.86 L
1.22T2 = 817.96
Divide both sides by 1.22
1.22T2/1.22 = 817.96/1.22
T2 = 670.459 K (Round to the nearest whole number as 670 K)
Thus, the temperature of the gas is 670 Kelvin
First a balanced reaction equation must be established:
→
Now if mass of aluminum = 145 g
the moles of aluminum = (MASS) ÷ (MOLAR MASS) = 145 g ÷ 30 g/mol
= 4.83 mols
Now the mole ratio of Al : O₂ based on the equation is 4 : 3
[
4Al +
3 O₂ → 2 Al₂O₃]
∴ if moles of Al = 4.83 moles
then moles of O₂ = (4.83 mol ÷ 4) × 3
=
3.63 mol (to 2 sig. fig.)
Thus it can be concluded that
3.63 moles of oxygen is needed to react completely with 145 g of aluminum.
The North American plate is moving towards the west-southwest at about 2.3 centimeters every year mediated by the Mid-Atlantic Ridge, the spreading center, which gave rise to the Atlantic Ocean. The small Juan De Fuca plate, moving east-northeast at 4 centimeters every year, was once a component of much greater oceanic plates known as the Farallon plate.
The Farallon plate used to comprise what is now the Cocos plate of Mexico and Central America, and the Juan de Fuca plate in the region from N. Vancouver Island to the Cape Mendicino California, and a big sea floor tract in between. However, the middle portion of the Old Farallon plate disappeared underneath North America, it was subducted underneath California leaving the San Andreas fault system behind as the contact between the Pacific plates and North America.
The Juan De Fuca plate is still actively subducting underneath North America. Its movement is not smooth, however, rather sticky. The buildup of strain takes place until the fault dissociates and a few meters of Juan De Fuca get slid underneath North America in a big earthquake.
