Answer to Question #53362 in Inorganic Chemistry for manisha




 Why tungsten have high melting point ?
Tungsten, also known as wolfram, is a hard, rare metal that is found naturally only in chemical compounds. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the elements.  
Tungsten in pure form has the highest melting point (3422 °C, 6192 °F), lowest vapor pressure (at temperatures above 1650 °C, 3000 °F) and the highest tensile strength. Tungsten has the lowest coefficient of thermal expansion of any pure metal. The low thermal expansion and high melting point and tensile strength of tungsten originate from strong covalent bonds formed between tungsten atoms by the 5d electrons. Alloying small quantities of tungsten with steel greatly increases its toughness.
an alloy is combination of a metal and a non metal. so it has partial characteristics of metal and non metal. being analloy the ions it it are randomly arranged. it does not have a specific arrangement of ions. hence the flow of electrons in this is more. the this feature of alloy leads to increase in resistivity due to free crystal lattice. we know that metals have high melting point but an alloy has low melting point beacause the presence of a non metal in it behaves as an impurity and restricts in raising to high melting point. due to high melting point the it takes a lot of current to melt and leads in slow movement of electrons which makes the device less efficient. therefore electronic device requires the metal of low melting point. an alloy plays the best role in the elctronic device like electric iron and heater. let's be clear, here: luminosity, "lumen output", "light output", or whatever you want to call the light intensity of a bulb is not a direct function of filament temperature. that's a gross ignorance and nothing more.
incandescents are rated by the power they use and nothing else. the color temperature is a function of the filament and the power applied. most filaments are tungsten so the filament can never heat above 3,700 kelvin, the melting point of tungsten.

so, most filaments are limited to 2,000 to 3,300 kelvin. this is the resulting color temperature and why some lights are whiter and some are more yellow., the latter tending to last longer since they are cooler or "warm" light.
in other words, a 100 watt bulb and a 40 watt bulb operate at the same filament temperature if they are both the same type of bulb, but the 100 watt bulb produces more of it. the "light output" , is not a function of filament temperature as veeyesvee and tony rb asserted.
so, a 60 watt bulb, tony, better produce more lumens than a 25 watt bulb, or what's the point of the other 35 watts? can someone design a really ineffecient transducer? sure... a toaster makes a terrible light source considering the power it consumes.
the real answer lies in the fact that the filament is not a linear resistance ( see below).

the hotter the bulb gets, the more efficient it becomes in producing light and a 60 watt bulb is about 14.2 lumens per watt where a 25 watt bulb is 8 lumens/watt.

the amount of light produced by a bulb depends on the ratings vs applied. since all you can vary is the voltage:
raise the voltage ratio to the 3.5 power to get equivalent luminosity.
life would be the -12th power of the voltage ratio.
and current is the .55 power of the voltage ratio.

(v2/v1)^3.5 = .235 (since 200lm/850lm = .235) 
(v2/v1)^3.5 = .235 ==> v2 = 120 * .661 = 79.34 volts

(v2/v1)^.55 = i2/.5 (60/120 = .5) ==> i2 = .398 a

79.34 x .398 = 31.6 w
or v2/v1 * (v2/v1) ^.55 = .52 power ratio and 60 * .52 = 31.6 w

so, the 60 watt bulb would need 32 watts of power to generate 200 lumen. molten sodium chloride because it is ionic and would have the strongest bonds of any of the liquids given is this a good answer?

when the electrons in the element are excited they jump to higher energy level and as the electrons fall back down it leave the excited state energy which is re-emitted, the wavelength of which is the emission spectrum. answer: oxygen gas is responsible for combustion. combustion is characterized as a rapid exothermic reaction that releases a significant amount of energy in the form of heat and flames as combustion reactions that can spread through a suitable medium. combustion is the outcome of dynamic or time-dependent activities between atoms, molecules, radicals, and solid boundaries at the molecular level. for combustion to occur, three conditions must be met, which are there should be a combustible material. there should be a supporter of combustion. the combustible material is heated to the ignition temperature. the presence of fuel has a significant effect. the existence of oxygen or air. the ignition temperature is kept constant. hi there!we are asked to determine the process corresponding to the increase in entropy labeled 1 and 2.we can use the heating curve to answer the given questions. recall that entropy is the degree of chaos or disorder of a system. for a given process, entropy (δs) will either increase or decrease. also, phase changes lead to a change in entropy:• we know that the phase at the highest temperature is gas• the plot has 2 process with drastic increase in entropy.• increase in entropy accompanying phase change is from solid → liquid → gas• therefore, the phases in the graph must have been:• phase change from solid to liquid is called fusion or melting• phase change from liquid to gas is called vaporizationprocess 1 represents melting (fusion), and 2 represents vaporization. reason: saturn has some unique characteristic like :-1. saturn has rings around it, these rings are made up of rocks, ice and dust.2. density of saturn is less than that of water (density is mass per unit volume), i.e. it is very light so if there were large enough ocean saturn would float on it. the percent ionization of nh3 will increase. yes, with fever, your temperature could rise above 99 degrees f. high industry areas could have issues with higher pollution problems with the air and water. high electrical plants might also cause emf problems for those that are sensitive to high electrical wave forms. there would also be more traffic in these areas and therefore, more potential for increased problems with pollution. see more...