1st Exam 2023 Chemistry Past Paper PDF

**Question:**\ Reaction of synthesis of ammonia at equilibrium:\ N2+3H2↔2NH3N\_2 + 3H\_2 \\leftrightarrow 2NH\_3N2​+3H2​↔2NH3​, ΔH=−92.3 kJ/mol\\Delta H = -92.3 \\, \\text{kJ/mol} ΔH=−92.3kJ/mol.\ What factors disturb equilibrium of this reaction and cause a net reverse reaction (shift the reaction...

**Question:**\ Reaction of synthesis of ammonia at equilibrium:\ N2+3H2↔2NH3N\_2 + 3H\_2 \\leftrightarrow 2NH\_3N2​+3H2​↔2NH3​, ΔH=−92.3 kJ/mol\\Delta H = -92.3 \\, \\text{kJ/mol} ΔH=−92.3kJ/mol.\ What factors disturb equilibrium of this reaction and cause a net reverse reaction (shift the reaction to the left)? **Alternatives:** 1. Removing reactants 2. Adding more reactants 3. Adding more products 4. Raising temperature 5. Lowering temperature 6. Rising pressure **Question:**\ The molar mass of NaOH is 40 g/mol. How many grams of NaOH should be added to water for the preparation of 0.5 L of a 500 mM solution? **Alternatives:** 1. 10 g 2. 50 g 3. 8 g 4. 5 g 5. 0.5 g A black and white math problem Description automatically generated with medium confidence **Question:**\ Which of the following statements about solutions is correct? Select one or more: **Alternatives:** 1. Real solution is always a homogeneous mixture. 2. A solution is formed when a solute dissolves in a solvent. 3. Regardless of the solute, the solvent must always be a liquid. 4. Substances with a similar molecular weight to the solvent will dissolve most readily. 5. The rule \"like dissolves like\" means that if the solvent and solute are both in the same phase (i.e., both liquids), they will dissolve most readily. **Question:**\ Hydrogen bonds form when a **hydrogen** atom in one OXYGEN molecule is attracted to the **electronegative** atom of another molecule **Question:\ Which of the following reactions is considered as a unimolecular reaction?** **Alternatives:** 1. **NO2​(gas)+CO(gas)→NO(gas)+CO2​(gas)** 2. **AgNO3​(liquid)+HCl(liquid)→AgCl(solid)+HNO3​(liquid)** 3. NH4​NO3​(solid)heating​NO2​(gas)+H2​O(gas( 4. NaOH(liquid)+HCl(liquid)→NaCl(liquid)+H2​O(liquid) **Question: MATCH**\ Classify each of these reactions: 1. ZnSO4​(aq)+Mg(s)→Zn(s)+MgSO4​(aq)\ This is a **bimolecular, heterogeneous reaction** because it involves two reactants (ZnSO4 and Mg) in different phases (solid and aqueous) 2. N2​O4​(g)→2NO2​(g)\ This is a **unimolecular, homogeneous reaction** because the decomposition involves a single molecule (N2O4) in a single phase (gaseous). 3. NaNO2​(aq)+HCl(aq)→NaCl(aq)+HNO3​(aq)\ This is a **bimolecular, homogeneous reaction** because it involves two reactants (NaNO2 and HCI) in the same phase (aqueous) **Question:**\ Which of the following statements about the rate of a chemical reaction is/are correct? **Alternatives:** 1. The presence of a catalyst will increase the number of molecules entering the transition state. 2. The surface area of solid reactants does not affect the reaction rate. 3. An increase in the concentration of reactants will increase the rate of chemical reaction. 4. The overall rate law is determined by the fastest step of a reaction. **Question:**\ Addition of 0.03 moles of HCl to 600 mL of phosphate buffer lowers the pH from 7.4 to 7.0. What is the buffering capacity for the acid? **Alternatives:** 1. 0.075 mol/L 2. 0.045 mol/L 3. 0.125 mol/L 4. 0.45 mol/L 5. 0.0125 mol/L  **Question:**\ 15 g of sugar was added to 120 g of a 20% sugar solution. What is the percent concentration of the resulting solution? **Alternatives:** 1. 12.5% 2. 25.9% 3. 29.2% 4. 28.9% 5. 32.5% A black background with white text Description automatically generated **Question:**\ The addition of a catalyst to a reaction: **Alternatives:** 1. Changes the enthalpy 2. Changes the nature of the products 3. Changes the activation energy 4. Changes the entropy **Question:**\ What is the charge of the granule in the micelle? The structure of the micelle in the colloidal solution is presented below. **Alternatives:** 1. Non-charged because of mAgl 2. Negative because of (n-x)NO3​ 3. Negative because of xNO3 4. Positive because of nAg+  A computer screen shot of a computer screen Description automatically generated **Question:**\ The enzyme carbonic anhydrase catalyzes the rapid conversion of CO2+H2O↔ H2​CO3​.\ What effect does doubling the amount of carbonic anhydrase have on equilibrium? **Alternatives:** 1. Accelerates reverse reaction in the direction of CO2​ formation and hyperventilation. 2. Accelerates forward reaction in the direction of H2CO3 formation. 3. Increases the rate of both forward and reverse reactions to the same extent. 4. No effect on equilibrium **Question:**\ What would you add to the aqueous solution of hydrofluoric acid (HF\\text{HF}HF) to form a buffer? **Alternatives:** 1. NaOH 2. HCl 3. KF 4. NaCl 5. NaF **Question:**\ Which of the following reactions can be considered as heterogeneous chemical reactions according to physical state? **Alternatives:** 1. NO2(gas)+CO(gas)→NO(gas)+CO2(gas 2. AgNO3(liquid)+HCl(liquid)→AgCl(solid)+HNO3(liquid) 3. NH4NO3(solid)→heatingNO2(gas)+H2O(gas) 4. NaOH(liquid)+HCl(liquid)→NaCl(liquid)+H2O(liquid) **Question:**\ Which of the following statements are correct about oncotic pressure? **Alternatives:** 1. It depends on the concentration of electrolytes. 2. It is the osmotic pressure due to the presence of electrolytes and solutes in plasma. 3. It is osmotic pressure exerted by albumin and other proteins. 4. Low oncotic pressure in plasma results in the expansion of interstitial fluid volume in tissues and edema. **Question:**\ Which of the following statements about jellification of high molecular mass compounds are correct? **Alternatives:** 1. Jellification is the process by which a solution of macromolecules loses its fluidity. 2. An increase in temperature results in a decrease in jellification. 3. Anions like chlorine, iodine promote jellification. 4. The size and shape do not affect jellification. **Question:**\ A buffer was made by combining 0.1 M of potassium benzoate and 0.1 M benzoic acid. After the addition of 0.05 M of HCl acid, the pH of the buffer will change to \_\_\_\_\_.\ (pKapK\_apKa​ of benzoic acid is 4.19). **Alternatives:** 1. 4.0 2. 4.67 3. 3.58 4. 4.19 5. 3.71  **Question:**\ Respiratory regulation of pH depends upon the: **Alternatives:** 1. Acetate buffer system. 2. Protein buffer system. 3. Phosphate buffer system. 4. Lactate buffer system. 5. Carbonic acid/bicarbonate buffer system. **Question:**\ Reaction of synthesis of ammonia at equilibrium: N2​+3H2​↔2NH3​,ΔH=−92.3kJ/mol(exothermic reaction). What factors disturb equilibrium of this reaction and cause a net forward reaction (shift the reaction to the right)? **Alternatives:** 1. Rising pressure 2. Lowering pressure 3. Adding more reactants 4. Raising temperature 5. Lowering temperature 6. Removing reactants **Question:**\ Which of the following properties are characteristic of colloid dispersion systems? **Alternatives:** 1. Low stability without stabilizing materials 2. Low dispersal degree 3. No contact area between dispersal phase and media 4. Tyndall effect 5. Dispersal phase has high affinity to dispersal media 6. Purified through semipermeable membrane **Question:** If 15 mL of 3.0 M HCl are diluted to a total volume of 100 mL, what is the new concentration? **Alternatives:** - \(a) 5 M - \(b) 0.45 M - \(c) 0.3 M - \(d) 3 M - \(e) 4.5 A screenshot of a black screen Description automatically generated **Question:** Addition of 0.05 moles of HCl to 0.5 L of ammonium buffer lowers the pH from 9.2 to 9.1. What is the buffering capacity of the acid? **Alternatives:** - \(a) 0.05 mol/L - \(b) 0.5 mol/L - \(c) 0.9 mol/L - \(d) 0.18 mol/L - \(e) 0.1 mol/L  **Question:** A student adds 6.00 g of a solid to the cone flask and adds water up to the 30.0 mL mark. The molar mass of the solid is 72.0 g/mol. What is the molarity (molar concentration) of the solution? **Alternatives:** - \(a) 5 mol/L - \(b) 0.00250 mol/L - \(c) 0.360 mol/L - \(d) 2.78 mol/L A black and white image of a black and white math equation Description automatically generated with medium confidence **Question:** Which of the following factors will result in increasing velocity (rate) of a chemical reaction? **Alternatives:** - \(a) Increasing in concentration of final reactants - \(b) Decreasing in concentration of initial reactants - \(c) Increasing in temperature - \(d) Decreasing in pressure **Question:** Normal blood plasma osmolarity is 0.3 Osm. What electrolyte should be used for infusions so that it is isotonic to the blood? **Alternatives:** - \(a) 0.1 M CaCl₂ - \(b) 0.1 M KCl - \(c) 0.1 M Glucose - \(d) 0.3 M NaCl **Question:** What will happen to a cell that is 70% water if it is in a solution of 30% water and 70% salt? **Alternatives:** - \(a) The cell would take in salt and swell. - \(b) The concentration of salt will reach a balance over time, thus the vital functions of the cell will not be affected. - \(c) The cell would take in water and swell. - \(d) The cell would lose water and shrink. **Question:** The micelle of the colloidal solution is: \[m(Mg(OH)2)nOH−(n−x)K+\]x+xK+ Effect of various salt solutions was examined on the stability of this colloidal solution. The data of this examination are presented in the table: **Predict which of the following ions is the most efficient inducer of coagulation:** - \(a) Na⁺ in Na₃PO₄ - \(b) SO₄²⁻ in MgSO₄ - \(c) PO₄³⁻ in Na₃PO₄ - \(d) Al³⁺ in AlCl₃ - \(e) Mg²⁺ in MgSO₄ **Question:** What mass of solute is present in 250 mL of a 0.100 mol/L solution of NaOH? Assume that NaOH has a molar mass of 40 g/mol. **Alternatives:** 1. 1.00 g 2. 1000 g 3. 0.625 g 4. 6.25 g 5. 10 g  **Question:** Sucrose dissolves well in water because: **Alternatives:** - \(a) Has a similar size to molecules of water - \(b) Forms covalent bonds with water - \(c) Separates into glucose and fructose - \(d) Is a polar molecule - \(e) It is bonded like a salt