It is True because in the periodic table of elements, there are seven horizontal rows of elements called periods. The vertical columns of elements are called groups, or families.
Answer: 22 neutrons
Explanation: 40 is the mass number = atomic mass = total number of protons and neutrons in atomic nucleus
18 is the number of protons in the nucleus of this atom
Then 40 - 18 = 22 neutrons
and this is Argon
Answer:
The correct answer is - A. Ethanol reduces air pollution.
Explanation:
Ethanol is believed to be better fuel for the environment than other petroleum fuels. Ethanol emits lower carbon dioxide as it is clean smokeless fuel, and produces less or the same oxides of nitrogen and hydrocarbons.
It is produced by the process of fermentation of molasses by yeast. Mixing it with the other fuels is found to be CO2 reduces by 30% of emissions to the atmosphere.
Answer: see figure attached and explanation below.
Explanation:
1) Chemical equation (given):
Fe + CuCl₂ → Cu + FeCl₂
2) ΔHf reactants: -256 kJ/mol (given)
3) ΔHf products: - 321 kJ/mol (given)
4) ΔH reaction = ΔHf products - ΔHf reactants = - 321 kJ/mol - (- 256 kJ/mol) = - 65 kJ/mol
5) Conclusion:
i) Since ΔHf of products is less (more negative) than ΔHf of reactants, the reaction is exhotermic: the reaction released energy, which is the reason why the products content less potential energy than the reactants.
ii) Then, the energy diagram is the typical one of an exothermic reaction: the products start a certain potential energy level, the energy incrases until reaching the activation energy (the energy barrier to form the activated complex) and then energy decreases until a level below the energy of the reactants.
iii) See the attached figure with such kind of diagram showing the products at a lower level than the reactans
Answer:
Percent error = 5.6%
Explanation:
Given data:
Measured value of density by students = 2.85 g/cm³
Accepted density of aluminium = 2.70 g/cm³
Percent error = ?
Solution:
Formula:
Percent error = [ Measured value - accepted value / accepted value ]× 100
Now we will put the values in formula:
Percent error = [ 2.85 g/cm³ - 2.70 g/cm³ / 2.70 g/cm³ ]× 100
Percent error = [0.15/2.70 g/cm³ ] × 100
Percent error = 0.056× 100
Percent error = 5.6%
