Light travels at precisely <span>299,792,458 metres every second (abbreviated to 3 x 10^8 metres every second but let's be precise) There are 60 seconds in every minute (</span><span>299 792 458 x 60 = 17,987,547,480m) 60 minutes in every hour (17,987,547,480 x 60 = 1,079,252,849,000m) 96 hours in 4 days (</span><span>1,079,252,849,000 x 96 = 10,360,827,350,000m) </span><span>Now let's convert to km to make this number (slightly) more manageable (</span>10,360,827,350,000 / 1000 = <span>103,608,273,500km) </span>Light travels <span>103,608,273,500km in 4 days - that's the equivalent of going around the equator of the earth 813,124 times!</span><span>
(i) Change in colour (ii) Change in temperature (iii) Formation of precipitate
Explanation:
(i) Change in colour: Reaction between lead nitrate solution and potassium iodide solution. Pb(NO3)2(aq)+2KI → PbI2(s)+2KNO3(aq) In this reaction, colour changes from colourless to yellow. (ii)Change in temperature: Action of dilute sulphuric acid on zinc. Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2 In this reaction, heat is evolved (iii) Formation of precipitate: Action of barium chloride on sodium sulphate. BaCl2(aq) +Na2SO4(aq) → BaSO4(s) +2NaCl(aq) BaSO4(s)
