What is higher calorific value (HCV) and Lower Calorific Value (LCV)?

What is higher calorific value (HCV) and Lower Calorific Value (LCV)?

Higher Calorific Value (HCV): When the steam in the exhaust gas is cooled to form water. The heat so liberated is adding up to the calorific value of the fuel. Hence, the calorific value in this case is known as higher calorific value (HCV) of the fuel. On the other hand, if the steam is let out along with the exhaust gas the calorific value of the fuel will be less and known as lower calorific value (LCV). For better understanding of analysis of the fuel just go through the other numerical problem given in this blog. 

The stoichiometric AFR by volume for combustion of CO is (a) 1.19

The stoichiometric AFR by volume for combustion of CO is

(a) 1.19, (b) 2.38, (c) 2.45 (d) 4.76

Solution: The reaction involved in the combustion of carbon mono-oxide (CO) is

2CO + O₂       à        2CO₂

                        2vol + 1vol    à     2vol of CO₂

So the combustion of 1vol of CO needs ½ volume of O₂

Now 21m³ of O₂ is present in 100 m³ of air

Therefore ½ m³ of O₂ will be present in ½*100/21=2.38 m³ of air

AFR = volume of air/ volume of fuel= 2.38/1=2.38

Hence the option (b) is correct.

Methane burns with stoichiometric quantity of air. The AFR ratio by weight is (a)13. 41

Methane burns with stoichiometric quantity of air. The AFR ratio by weight is

(a)13. 41, (b) 16.79, (c) 12.51, (d) 17.39

Solution: The reaction involved in the combustion of methane is

CH₄ + 2O₂ à CO₂ +2H₂O

Molar mass of methane is 16g

Molar mass of 2O₂ is 64g

It means, for combustion 16g methane needs 64g O₂ OR

1g of methane needs 64/16=4g of O₂

Therefore 1kg of methane needs 4kg of O₂

Now as we know 23kg of O₂ by mass is present in 100kg of air.

Therefore mass of air needed will be (100/23)*4=17.39kg of air

So AFR= Mass of air/Mass of fuel =17.39/1=17.39

So the option (d) is correct

If CH4 undergoes combustion with stoichiometric quantity of air, the AFR will be (a) 16.23

If CH4 undergoes combustion with stoichiometric quantity of air, the AFR will be

(a) 16.23, (b) 14.5, (c) 9.52, (d) 13.11

Determine AFR on the molar basis.

Solution:  The reaction involved in the combustion of methane is

CH₄ + 2O₂ à CO₂ +2H₂O

Here 1volume of methane needs 2 volume of O2

We know that in air there is 21% oxygen, which means

21m³ of oxygen is present in 100m³ of air

So 2m³ of oxygen present in (100/21)*2=9.52

AFR = mass of air/mass of fuel=9.52/1=9.52

What is Air-Fuel Ratio (AFR)? What is stoichiometric mixture?

What is Air-Fuel Ratio (AFR)? What is stoichiometric mixture?

Ans: Commonly abbreviated AFR stands for stands for Air-Fuel ratio which is the ratio of mass of air to mass of fuel present in the internal combustion engine. If the appropriate amount of air is provided to the engine so that the fuel burns completely then the ratio is known as stoichiometric mixture. AFR is very important as it is used in measurement for anti pollution and efficiency of engines. 

Modern periodic table

Modern periodic table

               OR

Draw modern periodic table.

               OR

With the help of modern periodic table explain group and periods.

               OR

Sketch the position of metals, non-metals and metalloid in the modern periodic table.

The vertical columns in the modern periodic table are known as groups. There are eighteen groups in the modern periodic table.
The horizontal rows in the modern periodic table are known as periods. There are seven rows in the modern periodic table.
The longest group of the modern periodic table is 6 which contain total of 32 elements.
In the above diagram of modern periodic table the green colored boxes shows the position of metals.
In the above diagram of modern periodic table the yellow colored boxes shows the position of  non-metals.
In the above diagram of modern periodic table the pink colored boxes shows the position of metalloids.
Metalloids are those elements which behave like metals as well as non-metals.

Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids

Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an Activity to prove it.
Answer: As shown in figure insert two nails on the wooden or rubber cork and place it in a beaker. Now connect these iron nails with a bulb, a 6 volt battery and a switch using a wire. Now pour some alcohol or glucose such that the nails will dip into it. Now turn the switch on, you will see that the bulb will not glow. Now empty the beaker and add some HCl aqueous solution at this time the bulb will glow. This proves that an acid can conduct electricity while alcohols and glucose cannot, even when they are containing hydrogen.

Above diagram shows that an acid solution can conduct electricity.

Difference between Metals and Non-metals on the basis of their physical properties

Difference between Metals and Non-metals on the basis of their physical properties:

Metals	Non-metals
1. Metals are generally solid at room temperature. (Except Mercury)	1. Non-metals exist in all the three states i.e solid liquid and gas.
2. Metals are generally hard. (except sodium which can be cut using a knife)	2. Non-metals are generally soft. (except diamond which us the hardest substance on the earth)
3. Metals are Malleable; means can be converted into thin sheets using a hammer. (except sodium and potassium)	3. Non-metals are generally brittle. Will broke down into pieces when beaten by a hammer.
4. Metals are ductile, means they can be converted into thin wires.	4. Non-metals are non ductile.
5. Metals have shiny surface or they are lustrous.	5. They are non lustrous. (except iodine)
6. Metals can lose electrons so they are electropositive in nature.	6. Non-metals gain electrons so they are electronegative in nature.
7. Metals are good conductors of heat and electricity.	7. Non-metals are bed conductors of heat and electricity. (Except graphite)
8. Metals are sonorous. They produce a sound on striking with a hard surface.	8. They does not do so they are not sonorous.
9. Metals generally have high densities. (except alkali metals)	9. Non-metals generally have low densities.

Explain sublimation

Explain sublimation.

Answer: Sublimation is the property of substance in which they are converted directly from solid to gas or vice versa. Such substances are known as sublime. Some examples of solids which sublime are ammonium chloride, camphor, naphthalene and anthracene. Let us perform an activity to separate a mixture of ammonium chloride and salt.

Take a mixture of ammonium chloride and salt in a china dish cover it inverted conical transparent funnel. At the other end of the funnel put a cotton plug so that vapour could not come out. Now place china dish on a burner. As the ammonium chloride is sublime after heating it will directly converted into vapour and this vapour will again condense at the upper colder part of funnel to form solid ammonium chloride. In this way the mixture ammonium chloride and salt can be separated by the sublimation method.

Electrolytic refining

Electrolytic refining:  It is the process of refining of metal in which impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of metal salt is used as an electrolyte. The apparatus is shown in the figure given below. When electric current is passed through the electrolyte, the impure metal from the anode is dissolved in the electrolyte and an equal amount of pure metal from the electrolyte is deposited on the cathode. The soluble impurities go into the solution whereas the insoluble impurities settle down at the bottom of the anode which is known as anode mud. Following diagram shows the electrolytic refining of copper in which anode is impure copper and cathode is thin strip of pure copper while the electrolyte used is the copper sulphate solution.

Test-Carbon and its Compound

                Science Test Class-X

                                                             Carbon and its Compound

                                  All questions are compulsory. All questions are of one mark.

1. Give the name of functional group (i) –CHO, (ii) –OH.
2. Name the product other than water formed on burning ethanol in air?
3. Name the functional group present in propanone (acetone).
4. Name the constituent of organic compound which can be produced by fermentation of sugar and is a constituent of beer.
5. Write (i) name and (ii) formula of the functional group present in the compound CH₃COOH.
6. What is denatured alcohol?
7. What happens when soap solution in a test tube is shaken with    (i) soft water (ii) Hard water?
8. What is catenation?
9. Write two allotropes of carbon besides Diamond?
10. Name the substance which is added to LPG for smell.
11. What is meant by saponification?
12.  Write the common and IUPAC name simplest aldehyde?
13. Write the structure formula of simplest ketone?
14. What are unsaturated hydrocarbons?
15. What is homologous series?
16. Number of covalent bond present if propane are_____.
17. Write the reaction of sodium hydroxide with ethanoic acid.
18. Write the dot structure of carbon dioxide.
19. What is hydrogenation?
20. What are the two ends when micelle is formed?