Quant Chemistry (MCQ Test)

Explanation
The molar mass of ZnO is 81.38 g/mol. In the carbon reduction method, carbon reacts with ZnO to produce Zn and CO. The balanced equation for the reaction is: ZnO + C -> Zn + CO. According to the equation, 1 mole of ZnO reacts with 1 mole of C to produce 1 mole of Zn. Therefore, the number of moles of Zn can be calculated by dividing the given mass of ZnO (9.15 g) by its molar mass (81.38 g/mol). The result is approximately 0.1125 moles. Since the molar ratio between ZnO and Zn is 1:1, the number of moles of Zn is also 0.1125. Finally, the mass of Zn can be calculated by multiplying the number of moles of Zn by its molar mass (65.38 g/mol), which gives a result of approximately 7.35 g.

Explanation
ফেনফথ্যালিন হল একটি মৃদু এসিড ও তীব্র ক্ষারের বিক্রিয়ায় উপযুক্ত নির্দেশক। এটি এসিড-বেস নির্দেশক হিসেবে ব্যবহার করা হয়। এর মাধ্যমে এসিড ও ক্ষারের পরিমাণ নির্ণয় করা যায়। এটি রঙের পরিবর্তন করে এসিড ও ক্ষারের নির্ণয় করার জন্য ব্যবহৃত হয়। সম্পূর্ণ বাক্যটির অর্থ হল, ফেনফথ্যালিন হল মৃদু এসিড ও তীব্র ক্ষারের বিক্রিয়ায় উপযুক্ত নির্দেশক।

Explanation
The oxidation state of Cl in Ca(OCl)Cl is +1 and -1. In the compound, the oxidation state of Ca is +2, and since the overall charge of the compound is 0, the sum of the oxidation states of all the elements must be 0. Therefore, the oxidation state of Cl must be such that when added to the oxidation state of Ca (+2), it gives a sum of 0. Since there are two Cl atoms, one Cl atom must have an oxidation state of +1 and the other Cl atom must have an oxidation state of -1 in order to satisfy this condition.

Explanation
The nature of the solution formed by mixing 0.1 M NaOH and H2SO4 will be acidic because H2SO4 is a strong acid and NaOH is a strong base. When they react, they will form H2O and Na2SO4, which is a salt. The presence of H2SO4 in the solution will make it acidic.

Explanation
The molar mass of O2 is 32 g/mol and the molar mass of CO2 is 44 g/mol. To find the mole fraction of CO2 in the mixture, we need to calculate the moles of CO2 and the total moles of the mixture.

The moles of O2 can be calculated by dividing its mass by its molar mass:
moles of O2 = 1.032 g / 32 g/mol = 0.03225 mol

The moles of CO2 can be calculated in the same way:
moles of CO2 = 0.573 g / 44 g/mol = 0.01302 mol

The total moles of the mixture is the sum of the moles of O2 and CO2:
total moles = 0.03225 mol + 0.01302 mol = 0.04527 mol

Finally, the mole fraction of CO2 can be calculated by dividing the moles of CO2 by the total moles:
mole fraction of CO2 = 0.01302 mol / 0.04527 mol = 0.287

Explanation
Fe2+ can function as both a reducing agent and an oxidizing agent. As a reducing agent, it can donate electrons to other substances and get oxidized in the process. As an oxidizing agent, it can accept electrons from other substances and get reduced in the process. This ability to undergo both reduction and oxidation reactions makes Fe2+ versatile and capable of acting as both a reducing agent and an oxidizing agent.

Explanation
The correct answer is 0.01 because the Beer-Lambert law states that the absorbance of a substance is directly proportional to the concentration of the substance in the solution. Therefore, a smaller value of absorbance (0.01) indicates a lower concentration of the solution, making it more applicable in the context of the Beer-Lambert law.

Explanation
The correct answer is 3-5. This pH range indicates that the color change of the methyl orange indicator occurs when the solution is acidic. Methyl orange is an acid-base indicator that changes color from red to yellow when the pH of the solution decreases. Therefore, a pH range of 3-5 suggests that the solution is acidic.

Explanation
In HPLC (High Performance Liquid Chromatography), methanol and water are commonly used as the mobile phase. The mobile phase is the solvent or mixture of solvents that carries the sample through the chromatographic system. Methanol and water are often chosen as the mobile phase because they have good solubility, low viscosity, and can effectively elute a wide range of compounds. Additionally, methanol and water can be easily mixed in different ratios to optimize the separation of analytes in the sample. Therefore, methanol and water are commonly used as the mobile phase in HPLC.

Explanation
The molar mass of NaHCO3 (sodium bicarbonate) is 84.01 g/mol. To find the molarity, we need to divide the given mass (3.5%) by the molar mass.

3.5% of NaHCO3 means 3.5 g of NaHCO3 in 100 g of solution.

So, the mass of NaHCO3 is 3.5 g.

Now, we can calculate the moles of NaHCO3 by dividing the mass by the molar mass:

moles = mass / molar mass = 3.5 g / 84.01 g/mol ≈ 0.04167 mol

Therefore, the molarity of 3.5% NaHCO3 is approximately 0.04167 M, which is equivalent to 0.4167 in the given options.

Explanation
In gas chromatography, a carrier gas is used to carry the sample through the column. The carrier gas should be inert and not react with the sample components. Among the given options, N2 (nitrogen gas) is the most suitable choice as it is inert and does not react with most compounds. O2 (oxygen gas) can react with certain compounds, Cl2 (chlorine gas) is highly reactive and can cause unwanted reactions, and H2 (hydrogen gas) is flammable and poses a safety risk. Therefore, N2 is the correct answer.

Explanation
The molar mass of K2Cr2O7 is 294.18 g/mol. To find the molarity, we need to divide the given mass (12.75 g) by the molar mass.

Molarity = mass/molar mass
Molarity = 12.75 g/294.18 g/mol
Molarity ≈ 0.043 mol/L

However, the question asks for the molarity in moles, not moles per liter. Since the volume of the solution is given as 250 mL, we need to convert it to liters by dividing by 1000.

Molarity = 0.043 mol/0.25 L
Molarity ≈ 0.17 mol

Therefore, the molarity of the solution is approximately 0.17 M.

Explanation
If 10g of CaCO3 is decomposed to form 2X10^20 particles, then the molar mass of CaCO3 can be calculated using Avogadro's number. The molar mass of CaCO3 is 100.09 g/mol. So, the number of moles of CaCO3 decomposed is 10g / 100.09 g/mol = 0.0999 mol. Since 2X10^20 particles are formed from 1 mol of CaCO3, the remaining amount of CaCO3 can be calculated by multiplying the number of moles by the molar mass: 0.0999 mol * 100.09 g/mol = 9.966 g. Therefore, the correct answer is 9.966 g.

Explanation
If 30% of the fertilizer used in the garden is in the form of P2O5, it means that 30% of the fertilizer is composed of phosphorus. Since P2O5 contains 44.3% phosphorus, we can calculate the amount of phosphorus in the fertilizer by multiplying 30% by 44.3%. This gives us 13.1%, which means that 13.1% of the fertilizer is composed of phosphorus. Therefore, the correct answer is 13.1%.

Explanation
K2Cr2O7 is the correct answer because it is the only compound in the given options that is a primary standard substance. Primary standard substances are highly pure and stable compounds that can be used to accurately determine the concentration of a solution in titration experiments. Na2S2O3, NaOH, and FeSO4 are not primary standard substances.

Explanation
The correct answer is "মোলারিটি" because it is the unit of concentration that measures the amount of a substance in a given volume of a solution. It is dependent on temperature as it represents the number of moles of solute per liter of solution. The other options, "মোল ভগ্নাংশ" and "মোলালিটি", are not units of temperature-dependent concentration.

Explanation
The question asks for the amount of CaO that can be obtained when 100g of limestone containing 5% impurities is heated at high temperature. Since limestone is mainly composed of CaCO3, the impurities will not contribute to the formation of CaO. Therefore, only 95% of the 100g of limestone will be converted to CaO. 95% of 100g is equal to 95g.

Explanation
In the given reaction, 1 mole of iodine is produced by the reaction between copper sulfate and potassium iodide. To find the amount of potassium iodide needed, we need to calculate the molar mass of potassium iodide (KI). The molar mass of KI is 39.1 g/mol (for K) + 126.9 g/mol (for I) = 166 g/mol. Therefore, to produce 1 mole of iodine, we need 166 g of potassium iodide. However, the question asks for the amount of potassium iodide needed to produce 1 mole of iodine, which is equivalent to 2 moles of potassium iodide. Therefore, we multiply the molar mass of KI by 2, which gives us 332 g. Hence, the correct answer is 332 g.

Explanation
When 50 g of urea is dissolved in 850 g of water, the volume of the solution is the sum of the volumes of urea and water. Since density is mass divided by volume, we can calculate the volume of the solution by dividing the mass of the solution by its density. The mass of the solution is 50 g + 850 g = 900 g. Therefore, the volume of the solution is 900 g / 0.9987 gm/cc = 900 cc. Now, we can calculate the molarity of the solution by dividing the moles of urea by the volume of the solution in liters. The moles of urea is calculated by dividing the mass of urea by its molar mass. The molar mass of urea (CH4N2O) is 60 g/mol. Therefore, the moles of urea is 50 g / 60 g/mol = 0.8333 mol. Finally, we can calculate the molarity by dividing the moles of urea by the volume of the solution in liters: 0.8333 mol / 0.9 L = 0.925 M. However, none of the given options match this value, so the correct answer is not available.

Explanation
To completely neutralize 12.25 gm of Na2CO3, we need to calculate the molar mass of Na2CO3. The molar mass of Na2CO3 is 106 g/mol. Since Na2CO3 is a base and HCl is an acid, they react in a 1:1 ratio. Therefore, we can use the equation:

mass of HCl = (molar mass of Na2CO3) / (molar mass of HCl) * mass of Na2CO3

Plugging in the values, we get:

mass of HCl = (106 g/mol) / (36.5 g/mol) * 12.25 gm

mass of HCl = 8.436 gm

Therefore, 8.436 gm of HCl is required to completely neutralize 12.25 gm of Na2CO3.

Explanation
The relative density of a substance is the ratio of its density to the density of water. In this question, the relative density of the sea water is given as 1.03. The amount of dry salt obtained from 1L of sea water is 38.5g. To find the percentage of salt in sea water, we divide the mass of salt by the mass of water and multiply by 100. Therefore, (38.5g/1000g) x 100 = 3.85%. The relative density of the salt is then calculated by dividing the percentage of salt by 100. So, 3.85/100 = 0.0385. Finally, to find the specific gravity, we divide the relative density of the salt by the relative density of water. Hence, 0.0385/1.03 = 0.0374 or 3.74%.

Explanation
When 25 cc of the solution is titrated with 24.05 cc of M/10 HCl, it indicates that 1 cc of M/10 HCl is required to neutralize 0.881 gm of Na2CO3. Therefore, to neutralize 1 gm of Na2CO3, (24.05/25) * 0.881 = 0.8464 gm of HCl is required. The molar mass of HCl is 36.5 gm/mol, so the molarity of HCl is (0.8464/36.5) mol/L. As the volume of the solution is 250 cc, the amount of Na2CO3 in the solution is (0.8464/36.5) * 250 = 5.853 grams. Therefore, the percentage of Na2CO3 in the solution is (5.853/18.02) * 100 = 32.23%.

Explanation
The molarity of a solution is defined as the number of moles of solute per liter of solution. In this case, the question asks for the molarity of a 0.1 N H2SO4 solution. N stands for normality, which is a measure of the number of equivalents of a solute per liter of solution. Since 0.1 N is equivalent to 0.1 moles per liter, the molarity of the solution will be M/10.

Explanation
The given question states that 27.5 mL of 0.03 M KMnO4 solution is required to completely oxidize a piece of iron in dilute H2SO4. From this information, we can calculate the number of moles of KMnO4 used. Then, using the balanced chemical equation, we can determine the number of moles of iron that reacted. Finally, using the molar mass of iron, we can calculate its mass. The correct answer is 0.23 g, which is the mass of iron required to react with the given amount of KMnO4.