CHEMISTRY
(1) What is the equation for reaction when calcium oxide and coke are heated in electric furnace
(2) what solid remains when the following is heated-(a) lithium trioxonitrate (v),
(b) potassium trioxonitrate (v), (c) calcium trioxonitrate (v).
(3) addition of water to calcium cabide leads to the formation of calcium hydroxide and ethane, write the equation for the production of ethyne.
(4) calculate the percentage by mass of silicon tetrachloride.
(5) ammonia phosphine are the hydride for the first two elements in group five draw a dot and cross diagram for the ammonia molecule.
(6) sketch and explain the shape of the ammonia molecule.
2a) LiNO3--2Li2O+4NO2+O2
(1) To find the equation for the reaction when calcium oxide and coke are heated in an electric furnace, we first need to understand the properties of these compounds.
Calcium oxide (CaO) is a metal oxide, also known as quicklime. Coke, in this context, refers to primarily carbon (C) material with impurities. When heated together in an electric furnace, a process called the "Blast Furnace Process" occurs.
The equation for the reaction of calcium oxide with coke can be written as follows:
CaO + 3C → CaC2 + CO
This reaction produces calcium carbide (CaC2) and carbon monoxide (CO).
(2) To determine the solid that remains when lithium trioxonitrate (V), potassium trioxonitrate (V), and calcium trioxonitrate (V) are heated, we need to understand the properties of these compounds and their decomposition reactions.
(a) Lithium trioxonitrate (V) also known as lithium nitrate (LiNO3) decomposes upon heating into lithium oxide (Li2O), nitrogen dioxide (NO2), and oxygen (O2).
The equation for this decomposition is:
2LiNO3 → 2Li2O + 4NO2 + O2
The solid remaining after heating lithium trioxonitrate (V) would be lithium oxide (Li2O).
(b) Potassium trioxonitrate (V), also known as potassium nitrate (KNO3), upon heating decomposes into potassium nitrite (KNO2) and oxygen (O2).
The equation for this decomposition is:
2KNO3 → 2KNO2 + O2
The solid remaining after heating potassium trioxonitrate (V) would be potassium nitrite (KNO2).
(c) Calcium trioxonitrate (V), also known as calcium nitrate (Ca(NO3)2), decomposes upon heating into calcium oxide (CaO), nitrogen dioxide (NO2), and oxygen (O2).
The equation for this decomposition is:
2Ca(NO3)2 → 2CaO + 4NO2 + O2
The solid remaining after heating calcium trioxonitrate (V) would be calcium oxide (CaO).
(3) When water is added to calcium carbide (CaC2), it produces calcium hydroxide (Ca(OH)2) and ethyne (C2H2), also known as acetylene.
The equation for the production of ethyne from calcium carbide and water is:
CaC2 + 2H2O → Ca(OH)2 + C2H2
(4) To calculate the percentage by mass of silicon tetrachloride (SiCl4), you need to know the atomic masses of silicon (Si) and chlorine (Cl) and apply the formula:
(Mass of SiCl4 / total mass of SiCl4) * 100
The atomic mass of silicon (Si) is about 28.09 g/mol, and the atomic mass of chlorine (Cl) is about 35.45 g/mol. The molecular mass of SiCl4 is the sum of these atomic masses.
So, to calculate the percentage by mass of SiCl4, you would need specific values in order to substitute them into the formula. For example, assuming the molar mass of SiCl4 is 169.89 g/mol, the calculation would be:
(169.89 g / 169.89 g) * 100 = 100%
However, if you have a different molar mass for SiCl4, the percentage by mass will vary accordingly.
(5) Ammonia (NH3) and phosphine (PH3) are both hydrides of elements in Group 5 of the periodic table. To draw the dot and cross diagram for ammonia (NH3), follow these steps:
- Identify the central atom, in this case, nitrogen (N).
- Determine the number of valence electrons for each atom involved: nitrogen has 5 valence electrons, while hydrogen (H) has 1 valence electron.
- Place one hydrogen atom on each side of the nitrogen atom, sharing a single covalent bond:
H - N - H
- Place two remaining hydrogen atoms on the top and bottom of the nitrogen atom, also sharing single covalent bonds:
H
|
H - N - H
|
H
- Finally, represent the shared electrons as dots or crosses between the respective atoms.
H
|
H : N : H
|
H
(6) The shape of the ammonia (NH3) molecule is trigonal pyramidal.
To explain the shape, we consider the arrangement of electron pairs around the central nitrogen atom. Ammonia has a total of 4 electron pairs around nitrogen: 3 bonding pairs and 1 lone pair.
Electron pairs repel each other and tend to maximize separation, resulting in the trigonal pyramidal shape. The 3 bonding pairs form a pyramid base, while the lone pair occupies the top position.
This shape ensures a tetrahedral orientation of electron pairs where the nitrogen atom is at the center, and the three hydrogen atoms are positioned symmetrically around it, giving ammonia its characteristic shape.