Energetics Questions and Answers

How much heat is needed to raise the temperature of 125 g of water (H₂O) from 7.2 °C to 36.4 °C? (c = 4.18 J/g °C) a) 4.3 J b) There is not enough information to answer this question. c) 3650 J d) 15257 J

Which of the following is the correct name given to describe the amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius? a) specific heat capacity b) none of these options is correct c) specific heat of reaction d) standard temperature of reaction

Which of the following chemical equations accurately represents an exothermic reaction? a) 2 NO2(g)->N2(g) + 2O2(g) ΔH = +68 kJ b) 2 NH3(g) +92 kJ → N2(g) + 3 H2(g) c) 2 H₂O(g) → 2 H2(g) + O2(g) + 482 kJ d) 1/2 N2(g) + 1/2O2(g)->NO(g) ΔH = + 88 kJ

A plo A plot of In K (equilibrium constant) for a reaction vs 1/T gave a line with slope - 2040 kelvin and a y-intercept of 2.41. What is the standard entropy change for the reaction? 20.04 J/mol.K 16.96 kJ/mol.K 24.10 J/mol.K 3.45 J/mol.K 16.96 J/mol.K

A calorimetry experiment determined that the combustion of 1.01 g of H₂(g) reacting with excess O₂(g) gave qsoln = 143 kJ. Calculate AH for the reaction: H₂(g) + 1/2O₂(g) → H₂O (0) AH = -9 AH = -143 KJ

Short Ride in a Fast Machine was composed by John Adams and is an example of Chance music Aleatory music Minimalistic music Liberation of sound music

A truck approaches a hill with a speed of 20 m/s. If the total mass of the truck with its load is 3,000 kg, what will be the kinetic energy of the truck? 200 kJ 500 kJ 400 kJ 600 kJ

Which instrument measures the absorption or release of heat in the calorimetric experiment? Thermometer Calorimeter Ammeter Galvanometer

Unlike charges each other. attract repel neither repel nor attract swap

The bicycle lamp glows when the bicycle's generator touches the wheel. This is because, electricity is generated as a result of electromagnetic induction electricity is generated as a result of eddy currents magnetic field is generated magnetic field is generated as a result of eddy currents

Which of the following enhances the static electricity? Rubbing objects together Moving objects Covering objects Joining objects together

Which of the following statements is correct? I. Static charges stay in one place. II. Batteries provide electricity. III. Like charges repel each other. IV. An open circuit will allow the electron flow. I, II, and III I, IV, and III I and III III and IV

Choose the correct answer. describes the amplification of the input force by a simple machine. Resistance force Efficiency Effort force Mechanical advantage

The states of matter are determined by the amount of ___ available. pressure energy temperature volume

You want to determine the specific heat capacity of a piece of ceramic. You find that it requires 14,006 J to heat a 48.4 g piece of the ceramic from 24.0°C to 114.2°C. What is the specific heat capacity of the ceramic (in J/g°C)? Your Answer: Answer units

YOU MUST SUBMIT WORK FOR THIS PROBLEM INTO A SEPARATE ASSIGNMENT. Use Hess's Law to calculate AHᵒrxn of: 2C(graphite) + O2(g) → 2CO(g) C(graphite) + O2(g) → CO2(g) 2CO(g) + O2(g) → 2CO2(g) The heat of reaction is (pay attention to the significant figures) AH°rxn=-393.5 kJ AH°rxn=-566.0 kj

QUESTION 29 YOU MUST SUBMIT WORK FOR THIS PROBLEM INTO A SEPARATE ASSIGNMENT. Hot pyrex (450. grams) is placed in 175.0 grams of water (d = 1 g/mL) which was at 21.0°C. What was the initial temperature of the pyrex (in °C) if the final temperature of the water and pyrex together was 31.0°C? Specific heat capacity of pyrex = 0.753 J/(g-K); water = 4.18 J/(g-K). The initial temperature is (pay attention to the significant figures)

Jaden used a claw hammer to pull a nail out of a piece of wood. He applied a force of 20 N on the handle of the claw hammer. The force exerted on the nail in the claw is 80 N. What is the mechanical advantage of the claw hammer? 0.5 01.0 2.0 4.0

Hot gypsum (242. grams) is placed in 125.0 grams of water (d = 1 g/mL) which was at 21.0°C. What was the initial temperature of the gypsum (in °C) if the final temperature of the water and gypsum together was 29.0°C? Specific heat capacity of gypsum = 1.090 J/(g-K); water = 4.18 J/(g-K). The initial temperature is__ °℃

A system releases 32.3 kJ of heat while having 12.2 kJ of work done on it by the surroundings. What is the change in energy of the system (AE)? +2.65 kJ +20.1 kJ -20.1 kJ +44.5 kJ -44.5 kJ

Consider the following reaction: CaO(s) + 3C(s)→→ CaC2(s) + CO(g) AH°rxn = +464.8 kJ Molar masses (g/mole): Cao(s) = 56.08;IC(s) = 12.01; CaC₂(s) = 64.10; CO(g) = 28.01 How much heat (in kJ) is absorbed in a reaction in which 123.4 grams of C(s) is reacted under these conditions? The heat absorbed in the reaction is kj (pay attention to the significant figures)

What is the final temperature of water and aluminum if 75 g of aluminum with an initial temperature of 350. K is paced in 13.89 moles of water which was at 20.0°C. Specific heat capacity of aluminum = 0.921 J/(g-K) and water = 4.18 J/(g.K)

Consider the following thermochemical equation: N2(g) + 4H2O(1)→ N2H4(1) + 2H2O2(1) AH°rxn = +818.2 kJ What is true if the reverse reaction occurs and 1.25 moles of H₂O2(1) reacts with excess N₂H4(1) to form N2(g) and H₂O(l)? 511 kJ of energy will be released 511 kJ of energy will be absorbed 256 kJ of energy will be released 256 kJ of energy will be absorbed 1020 kJ of energy will be absorbed

Be sure to answer all parts. What is the change in internal energy (in J) of a system that absorbs 0.669 kJ of heat from its surroundings and has 0.864 kcal of work done on it? Give your answer in scientific notation. x 10

An unknown volume of water at 18.2°C is added to 16.4 mL of water at 35.0°C. If the final temperature is 23.5°C, what was the unknown volume? (Assume that no heat is lost to the surroundings; d of water is 1.00 g/mL.) __mL

A system receives 475 J of heat and delivers 475 J of work to its surroundings. What is the change in internal energy of the system (in J)?

One piece of copper jewelry at 119°C has exactly twice the mass of another piece, which is at 35°C. Both pieces are placed inside a calorimeter whose heat capacity is negligible. What is the final temperature inside the calorimeter (c of copper = 0.387 J/g-K)? __C

High-purity benzoic acid (C6H5COOH; AHrxn for combustion = -3227 kJ/mol) is used as a standard for calibrating bomb calorimeters. A 1.221-g sample burns in a calorimeter (heat capacity = 1365 J/°C) that contains exactly 1.350 kg of water. What temperature change is observed? °C

Phosphorus pentachloride is used in the industrial preparation of organic phosphorus compounds. Equation 1 shows its preparation from PC13(0) and Cl₂(g): (1) PCl3(l) + Cl₂(g) → PCl5(g) Use equations (2) and (3) to calculate ΔHn of equation (1): (2) P4(s) + 6Cl₂(g) → 4PC13(l) ΔH = -1280 kJ (3) P4(s)+10Cl₂(g) → 4PCL5(g) ΔH=-1774 kJ

What mass (in g) of carbon monoxide must be burned to produce 175 kJ of heat under standard state conditions if the enthalpy of combustion is -283.0 kJ/mol? CO(g) + O₂(g) -> CO₂(g) [unbalanced]

Enter your answer in the provided box. A 287-g aluminum engine part at an initial temperature of 17.69°C absorbs 92.2 kJ of heat. What is the final temperature of the part (e of Al=0.900 J/g-K)? __C

The energy E of the electron in a hydrogen atom can be calculated from the Bohr formula: E= -Ry/n2 In this equation R, stands for the Rydberg energy, and n stands for the principal quantum number of the orbital that holds the electron. (You can find the value of the Rydberg energy using the Data button on the ALEKS toolbar.) Calculate the wavelength of the line in the absorption line spectrum of hydrogen caused by the transition of the electron from an orbital with n=5 to an orbital with = 11. Round your answer to 3 significant digits.

Calculate the lattice energy, Δlattice U, of LiBr(s), Li'(g) + Br(g) ⇒ LiBr(s) Δlattice U = ? given the following thermochemical equations. Enthalpy of formation of Li(g) +159 kJ/mole Enthalpy change for Li(g)Li*(g) + e +513 kJ/mole Enthalpy of formation of Br(g) +112 kJ/mole Enthalpy change for Br(g) + e- ⇒Br(g) -325 kJ/mole Enthalpy of formation of LiBr(s) -356 kJ/mole A. -815 KJ B. +103 kJ C. -215 kJ D. +815 KJ E. +215 KJ

Compounds of boron and hydrogen are remarkable for their unusual bonding and also for their reactivity. With the more reactive halogens, for example, diborane (B₂H6) forms trihalides even at low temperatures: B₂H6(g) + 6 Cl₂(g) → 2 BCl3(g) + 6 HCl(g) ΔHrxn=-755.4 kJ How much heat is released when 3.621 kg of diborane reacts? (Give your answer in scientific notation.) __ x 10 __ kJ kJ

Thermal decomposition of 5.00 metric tons of limestone to lime and carbon dioxide requires 9.00 x 106 kJ of heat. Convert this energy to (a) joules; (b) calories; (c) British thermal units. Give your answers in scientific notation. (a) __x 10___ J (b)__ x 10__ cal (c)__x __10 btu

Be sure to answer all parts. Deterioration of buildings, bridges, and other structures through the rusting of iron costs millions of dollars every day. Although the actual process also requires water, a simplified equation (with rust shown as Fe₂O3) is: 4 Fe(s) + 3 O₂(g) → 2 Fe₂O3(s) ΔHxn=-1.65 × 10³ kJ (a) What is the AHrn when 0.250 kg of iron rusts? __x 10__kJ __x__ 10__g Fe₂O3 (b) How much rust forms when 8.60 × 10³ kJ of heat is released?

A 33.7-g sample of an alloy at 93.00°C is placed into 50.0 g of water at 22.00°C in an insulated coffee- cup calorimeter with a heat capacity of 9.20 J/K. If the final temperature of the system is 31.10°C, what is the specific heat capacity of the alloy?

Be sure to answer all parts. Consider the following balanced thermochemical equation for a reaction sometimes used for H₂S production: 1/8Sg(s) + H₂(g) → H₂S(g) ΔHrxn=-20.2 kJ (a) Is this an exothermic or endothermic reaction? exothermic endothermic (b) What is AHrxn for the reverse reaction? kJ (c) What is AH when 1.40 mol of Sg reacts?

Calculate AHxn for 2NOCI(g) → N₂(g) + O₂(g) + Cl₂(g) given the following set of reactions: 1/2 N₂(g) + 1/2 O₂(g) → NO(g) ΔHrxn= 90.3 kJ NO(g) + 1/2 Cl₂(g) → NOCI(g) ΔHrxn=-38.6 kJ

Enter your answer in the provided box. An unknown volume of water at 18.2°C is added to 27.5 mL of water at 35.0°C. If the final temperature is 23.5°C, what was the unknown volume? (Assume that no heat is lost to the surroundings; d of water is 1.00 g/mL.) mL

When someone is injured, responding medical personnel may use either hot packs or cold packs to treat the injuries. These are examples of miniature chemical reactions. Using hot packs and cold packs as an example, explain the terms endothermic reaction and exothermic reaction.

For which of the following reactions would the heat of reaction be labeled AH₂ ? (A) PC13(g) + 1/2O2(g) → POC13(g) (B) CaO () + SO2(g) → CaSO3(g) (C) Als) + 3/2 O2(g) + 3/2 H2(g)→ Al(OH)3(6) (D) 1/2 N₂O(g) + 1/4 O2(g) → NO(g) (E) All these reactions would be labeled AH,

Walking at a brisk pace burns off about 280 Cal/h. How long would you have to walk to burn off the Calories obtained from eating a cheeseburger that contained 27 g of protein, 25 g of fat, and 29 g of carbohydrates? [Hint: One gram of protein or one gram of carbohydrate typically releases about 4 Cal/g, while fat releases 9 Cal/g.]

C Solve for the final pressure in terms of the original pressures of helium and neon. Assume temperature is constant. (Select all that apply.) 5/4PHe,original 3/5PNe,original 5/6PNe,original 5/6PHe,original 5/4PNe,original 2/5PHe, original

During a reaction, the enthalpy of formation of an intermediate is 90.3 kJ/mol. During the reaction, 2 moles of the intermediate are formed as a reactant. What is the enthalpy value for this step of the reaction? A. 90.3 kJ B.-90.3 kJ C. 180.6 kJ D. -180.6 kJ

If it takes 37.0 calories of heat to raise the temperature of 13.2 g of a substance 8.50°C, what is the specific heat of the substance? Specific heat = cal/g. °C

One serving (25 grams) of regular trail mix contains 8 g of fat, 13 g of carbohydrates, and 4 g of protein. Estimate the number of calories. [Hint: One gram of protein or one gram of carbohydrate typically releases about 4 Cal/g, while fat releases 9 Cal/g.] Report your answer to 1 significant figure. cal

Enter your answer in the provided box. Use the heat of fusion of water, 79.7 cal/g, to answer the following question. How much energy in kilocalories is absorbed when 26.0 g of water melts? kcal

cess important values i Calculate the energy of an electron in the n=4 level of a hydrogen atom. Energy = Joules

A-can of soda contains 130 Calories, and no protein or fat. How many grams of carbohydrates are present in each can? [Hint: One gram of protein or one gram of carbohydrate typically releases about 4 Cal/g, while fat releases 9 Cal/g.] Report your answer to 1 significant figure.