NEET Question Paper Solved 2018. In this blog, we will be solving the NEET 2018 question paper and providing step-by-step solutions for each question. This will be an excellent resource for the students who are preparing for the NEET exam, as it will help them understand the concepts better and give them an idea of the type of questions they can expect in the exam.
1. The current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage
applied) is 20 div/V. The resistance of the galvanometer is
(1) 250 Ω
(2) 25 Ω
(3) 40 Ω
(4) 500 Ω
The sensitivity of a moving coil galvanometer relates the angular deflection of the needle to the current passing through it. The sensitivity can be expressed as the number of divisions (or degrees) of deflection per unit current (in mA).
In this case, the sensitivity is 5 div/mA, which means that if a current of 1 mA passes through the galvanometer, the needle will deflect by 5 divisions.
The voltage sensitivity of the galvanometer relates the angular deflection of the needle to the voltage applied across it. The voltage sensitivity can be expressed as the number of divisions (or degrees) of deflection per unit voltage (in V).
In this case, the voltage sensitivity is 20 div/V, which means that if a voltage of 1 V is applied across the galvanometer, the needle will deflect by 20 divisions.
The resistance of the galvanometer can be calculated using the formula:
Resistance = Voltage / Current
We can rearrange this formula to solve for the resistance:
Resistance = Voltage / Current Resistance = (1 V) / (1 mA / 1000) Resistance = 1000 Ω
However, this is the total resistance of the galvanometer and the shunt resistor (if used). Since the sensitivity is given for the galvanometer alone, we need to subtract the shunt resistance from the total resistance to get the resistance of the galvanometer alone.
Let’s assume that a shunt resistor is not used, so the total resistance is equal to the resistance of the galvanometer alone. Therefore, the resistance of the galvanometer is:
Resistance = 1000 Ω – 0 Ω (assuming no shunt resistor) Resistance = 1000 Ω
So the answer is (4) 500 Ω (assuming no shunt resistor).
2. In a p-n junction diode, a change in temperature due to heating
(1) does not affect the resistance of the p-n junction
(2) affects only forward resistance
(3) affects only reverse resistance
(4) affects the overall V – I characteristics of the p-n junction
In a p-n junction diode, a change in temperature due to heating can affect the overall V-I (voltage-current) characteristics of the diode, which is an option (4).
When a p-n junction diode is heated, it can cause changes in the behavior of the charge carriers in the device, leading to changes in the forward and reverse bias characteristics. For example, heating can increase the number of thermally generated charge carriers in the device, which can affect the reverse bias breakdown voltage.
In addition, heating can affect the diode’s saturation current, which can change the forward resistance of the diode. The forward resistance of the diode decreases with an increase in temperature, which means that the diode conducts more current for a given voltage.
Therefore, heating can have a significant impact on the overall V-I characteristics of a p-n junction diode, affecting both the forward and reverse bias characteristics. It’s essential to consider the effect of temperature on the diode’s behavior when designing circuits that use p-n junction diodes.
3. Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of (X) is 1s2 2s2 2p3, the simplest formula for this compound is.
To form an ionic compound, magnesium will lose two electrons to attain a stable octet configuration, becoming an Mg2+ ion.
The element X will gain two electrons to attain the noble gas configuration of neon, becoming X2-.
The electron configuration of X is: 1s2 2s2 2p3
By gaining two electrons, the electronic configuration of X2- will be:
1s2 2s2 2p6
The ionic compound formed between Mg2+ and X2- will have a neutral overall charge.
The ratio of the cation and anion in the ionic compound must be such that the positive and negative charges balance out.
Therefore, the simplest formula for the compound is MgX2, option (2).
4. The correction factor ‘a’ to the ideal gas equation corresponds to.
(1) electric field present between the gas molecules
(2) volume of the gas molecules
(3) density of the gas molecules
(4) forces of attraction between the gas molecules
The correction factor ‘a’ in the van der Waals equation of state corresponds to the forces of attraction between gas molecules.
The ideal gas equation of state assumes that gas molecules have no volume and no intermolecular forces. However, real gas molecules do have some volume and there are attractive forces between them, which cause them to deviate from ideal gas behavior at high pressures and low temperatures.
The van der Waals equation of state corrects for these deviations by incorporating two correction factors, ‘a’ and ‘b’. The correction factor ‘a’ accounts for the attractive forces between gas molecules, while ‘b’ accounts for their volume.
Therefore, the correct answer is (4) forces of attraction between the gas molecules.
5.Iron carbonyl, Fe(CO)5 is
Iron carbonyl, Fe(CO)5, is a mononuclear compound.
“Mono-” means one, so mononuclear means that the compound contains one nucleus or central metal atom. In this case, the central metal atom is iron (Fe).
The carbonyl ligands (CO) are attached to the iron atom and surround it in a single cluster. Each carbonyl ligand is coordinated to the iron atom through the carbon atom, forming a complex with Fe(CO)5 stoichiometry.
Therefore, the correct answer is (2) mononuclear.
6. Which of the following compounds can form a zwitterion?
(1) Benzoic acid
A zwitterion is a molecule with both a positive and a negative charge, which cancels each other out, resulting in a neutral molecule. It contains at least one acidic functional group (such as a carboxylic acid) and one basic functional group (such as an amino group) that can react with each other to form an internal salt.
Out of the given options, only glycine has both an acidic carboxylic acid group (-COOH) and a basic amino group (-NH2) in the same molecule. When glycine is in a neutral pH environment, the carboxylic acid group will donate a proton (H+) to the amino group to form an internal salt, resulting in a zwitterion with both a positive charge on the nitrogen and a negative charge on the carboxylate group.
Benzoic acid has a carboxylic acid group but no basic functional group, so it cannot form a zwitterion. Acetanilide has an amide group, which can act as a weak base, but it does not have an acidic group to form a zwitterion. Aniline has a basic amino group, but no acidic group to react with it to form a zwitterion.
Therefore, the correct answer is (4) glycine.