The exhaust composition when using hydrogen as fuel in motor vehicles*1 pointCarbon dioxideCarbon monoxideWater

What is the only by-product of burning Hydrogen fuel?*Carbon monoxideMethaneWaterCO2

Why hydrogen is not recommended to use as fuel in direct internal combustion engine?*1 pointBecause of low ignition and high combustion energyBecause of high ignition and low combustion energyBecause low ignition and low combustion energy

Which of the following is not produced as exhaust of vehicles?(1 Point)sulphur dioxidecarbon dioxidecarbon monoxidefly ashNatural sink of stratospheric ozone layer is(1 Point)SO2HCFFreonsSulphur flux of oceansSubstances that are easily broken down into harmless substances by decomposers are termed:(1 Point)environmentally unfriendlybiodegradablenon-biodegradableNone of theseToday, concentration of greenhouse gases is high because of(1 Point)use of refrigeratorincreased combustion of oil and coaldeforestationall of the aboveWhich of the following is usually not classified as atmospheric pollutant?(1 Point)CO2CONOxSO2

Combustion occurs when an oxidation-reduction reaction takes place between a reduced fuel source and an oxidizer, most frequently oxygen.  The reaction between hydrogen and oxygen forms water (Reaction 1) and is highly exothermic and thermodynamically favorable.  At the completion of hydrogen combustion, essentially all H2 molecules have been converted to water.  Nevertheless, at room temperature and atmospheric pressure, molecular hydrogen and oxygen can coexist quite stably.2 H2(g) + O2(g) → 2 H2O(g)Reaction 1A group of researchers designed two prototype internal combustion engines, each of which could inject a hydrogen/oxygen mixture into a 5-mL combustion chamber at a total pressure of 1 atm and could repeat this process for several cycles.  In one engine design, a spark was generated to initiate combustion as hydrogen and oxygen were injected.  In another method, the combustion chamber was coated with a small amount of platinum powder.  Platinum dramatically increases the reaction rate at room temperature without the need for a spark.  The platinum itself is not altered by the reaction and can be reused.  Researchers measured the maximum power output of both engine designs under identical injection and temperature conditions (Figure 1).Figure 1  Relative power outputs of hydrogen engines with different ignition sources at 298 KThe power output of an engine is directly related to the rate of combustion.  In the presence of platinum, researchers measured the engine's rate of water production at various temperatures and H2/O2 mixture compositions.  The results are shown in Figure 2.Figure 2  Rate of combustion in platinum-coated engines under various conditionsAdapted from Schultze, M., Mantzaras, J. (2013) Hetero-/homogeneous combustion of hydrogen/air mixtures over platinum: Fuel-lean versus fuel-rich combustion modes. International Journal of Hydrogen Energy, Vol. 38, Issue 25, 10654-10670. Question 11Platinum most likely increases the reaction rate by stabilizing:A.the reactants.B.the products.C.the intermediate step.D.the transition state.

Question 16: VerticalCOMPREHENSIONRead the following unedited passage and pick the statement(s) that is/are accurate among the options provided.The environment is negatively affected by emissions of conventional internal combustion (IC) engines, since they emit a lot of greenhouse gases and other harmful pollutants. This necessitates the search for alternative fuels with low carbon emissions for IC engines [1–2]. Hydrogen, a clean and renewable resource, is considered a promising candidate by many researchers [3–5]. Automobile manufacturers have developed hydrogen-fueled internal combustion engines (HICEs) and tests have shown that HICEs have good power performance and reliability, with almost zero carbon emissions [6–10]. However, NOX is one of the major pollutants emitted by HICEs. HICEs usually generate large amounts of NOX emissions under high loads, which is an inevitable phenomenon and is attributed to the temperature rise in the cylinder [11–14]. Technologies such as lean burn, retarded ignition, and exhaust gas recirculation have been found to be effective in reducing NOX emissions. These studies have investigated the variation in NOX emissions with changes in the control parameters of IC engines, using experimental methods. However, the mechanism of NOX formation has not been discussed in sufficient detail.Conventional internal combustion (IC) engines emit large quantities of greenhouse gases and other harmful pollutants, which have an adverse impact on the environment.In their search for alternative fuels that use less carbon in IC engines, researchers have found that hydrogen can be used to create a fuel that may be considered promising.Because of the temperature rise in the cylinder, HICEs generate a lot of NOX emissions under high loads through lean burn, retarded ignition, and exhaust gas recirculation.In some previous studies, researchers have focused on how NOX emissions vary with changes in the control parameters of IC engines, using experimental methods, but the mechanism of NOX formation needs to be investigated further.