Free Scientific Reasoning MCQs with Answers

301. Isomers are molecules or polyatomic ions with identical molecular formula - that is, same number of atoms of each element - but distinct arrangements of atoms in space. Isomerism refers to the existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural or constitutional isomerism, in which bonds between the atoms differ; and stereoisomerism or spatial isomerism, in which the bonds are the same but the relative positions of the atoms differ. How many chain isomers can an aliphatic saturated hydrocarbon with 7 carbons make?

• A. 7
• B. 5
• C. 12
• D. 64

Explanation: An aliphatic saturated hydrocarbon with 7 carbons is a type of alkane, and its general formula can be represented as CₙH₂ₙ₊₂, where n is the number of carbon atoms. For an alkane with 7 carbons, the formula is C₇H₁₆. Now, let's consider the possibilities for chain isomerism in alkanes. In chain isomerism, the carbon atoms can be arranged in different ways. The number of chain isomers for an alkane with n carbon atoms can be determined using the formula 2n-1. For C₇H₁₆: Number of chain isomers = 27-1 = 26 = 64 So, the correct answer is 64.

302. Based on Table 1, the dielectric that fills the PPC shown in Figure 1 is most likely which material?

• A. Polystyrene
• B. Paper
• C. Pyrex glass
• D. SrTiO3

Explanation: According to the diagram given, the value of Co is 2 so 2 x K=10.4 where K is approximately 5. Now refer to table 1 where the values of K are given. Looking at the options available pyrex glass is the most suitable answer as it has a K value of 5.2.

303. When choosing a suitable metal for use in overhead electrical cables, engineers prefer a metal for which the expression (Density) x (Resistivity) has as small a value as possible. Based on table 1, which of the following metals would be the most suitable for use in an overhead cable?

• A. Aluminum
• B. Copper
• C. Gold
• D. Silver

Explanation: According to the values given in the table, aluminium has the lowest calculated value for (density)x(resistivity)

304. The diagram below shows a wire carrying conventional current in the direction shown by the red arrows. The magnetic filed is straight downward, as indication by the blue X's. What is the direction of the force exerted by the magnetic field on the wire?

• A. Upward
• B. Downward
• C. Right
• D. Left

Explanation: According to flemming's left hand rule, the direction of force will be downwards.

305. In human blood, calcium (Ca2+) concentration is regulated by vitamin D3. First vitamin D3 is converted to calcidiol (CD) in the liver. An elevated concentration of CD inhibits furhter conversion of vitamin D3. Next, CD is conceverted to calcitriol (CT) in the kidneys in a reaction tht requires parathyroid hormone (PTH). An elevated concentration of CT increases Ca2+ concentration, which in turn inhibits further release of PTH. See figure 1 According to Figure 3, the relative blood CT concentration is between 5 times normal and 6 times normal within which of the following blood Ca2+ concentration ranges?

• A. 8mg/100 mL to 9mg/100 mL
• B. 10mg/100 mL to 11 mg/100 mL
• C. 11mg/100 mL to 12mg/100 mL
• D. 13mg/100 mL to 14mg/100 mL

Explanation: Looking at figure 3, it is clear that only at blood Ca2+ concentration range of 8mg/100 mL to 9mg/100 mL, the relative blood CT concentration is between 5 times normal and 6 times normal.

306. According to the given information, the inhibition of the conversion of vitamin D3 to CD is caused by

• A. A low concentration of CT
• B. A low concentration of CD
• C. An elevated concentration of CT
• D. An elevated concentration of CD

Explanation: The question states 'An elevated concentration of CD inhibits furhter conversion of vitamin D3.' Thus D is the correct answer

307. A solute is any substance that is dissolved in another substance, which is called the solvent. A student tested the solubility (a measure of how much solute will dissolve into the solvent) of six different substances. The solubility of a substance at a given temperature is defined as the concentration of the dissolved solute that is in equilibrium with the solvent. Table 1 represents the concentration of dissolved substances in 100 grams of water at various temperatures. The concentrations are expressed in grams of solute per 100 grams of water. According to the table, the concentrations of which of the following substances varies least with temperature

• A. HCl
• B. NH3
• C. NaCl
• D. KCl

Explanation: The best answer is C. The question asks you to look at the overall trends of the data sets for each substance. A good way to measure the degree to which data varies would be to find the range, meaning subtract the lowest value from the highest value for each individual substance. In this problem it is clear that NaCl varies the least with temperature.

308. A solute is any substance that is dissolved in another substance, which is called the solvent. A student tested the solubility (a measure of how much solute will dissolve into the solvent) of six different substances. The solubility of a substance at a given temperature is defined as the concentration of the dissolved solute that is in equilibrium with the solvent. Table 1 represents the concentration of dissolved substances in 100 grams of water at various temperatures. The concentrations are expressed in grams of solute per 100 grams of water. The graph below best represents the relationship between concentration and temperature for which of the following substances?

• A. HCl
• B. NH3
• C. NaCl
• D. KCl

Explanation: The best answer is a. In this question you are asked to look at the trends of the substances, especially at how their concentrations change with increasing temperature. In the data set, some substances become more soluble with increasing temperature, while some become less soluble. The graph represents the solubility curve for a substance that gets less soluble with increasing temperature. Looking at the possible answer choices, HCl is the only logical choice.

309. A solute is any substance that is dissolved in another substance, which is called the solvent. A student tested the solubility (a measure of how much solute will dissolve into the solvent) of six different substances. The solubility of a substance at a given temperature is defined as the concentration of the dissolved solute that is in equilibrium with the solvent. Table 1 represents the concentration of dissolved substances in 100 grams of water at various temperatures. The concentrations are expressed in grams of solute per 100 grams of water. According to table 1, HCl would most likely have what concentration at 70 degree C?

• A. 25.5 g/100g H2O
• B. 37.0 g/100g H2O
• C. 48.5 g/100g H2O
• D. 51.5 g/100g H2O

Explanation: The best answer is d. According to Table 1, HCl has a concentration of 55 g/100 g H2O at 60◦C, and a concentration of 48 g/100 g H2O at 80◦C. Therefore, at 70◦C it would likely have a concentration of 55 + 48 ÷ 2 = 51.5 g/100 g H2O.

310. The atmosphere is made up of 4 distinct layers: the troposphere, stratosphere, mesosphere, and thermosphere. Different types of clouds form in the different layers depending on the pressure in the atmosphere and the ambient temperature. The cloud types include nimbus, stratus, cumulus, and cirrus. Figure 1 shows the location of the barriers of the atmosphere when the temperature and pressure are at an ideal condition for cloud formation. It also shows the different types of clouds formed at the different levels. Note: Clouds are formed mostly of water crystals, but can also contain particles of rock and dust. According to fig 1 as pressure within the atmosphere layers increases, temperature within the atmospheric layers

• A. Increases only
• B. Decreases only
• C. Increases upto 6 psi, then decreases
• D. Decreases upto 10 psi then increases

Explanation: The key in Figure 1 includes two lines: temperature and pressure. As the pressure line is increasing (positive slope), the temperature line is decreasing (negative slope). This suggests that as pressure within the atmospheric layer increases, temperature decreases only, answer choice B.