Dimitri Mendeleev was the first to put elements together on a table. He knew there were elements missing but he noticed a trend in some of the elements known at the time. Sodium, Lithium and other alkali metals all have the same properties so he put them under the same column and created other columns with similar attributes (Halogens, Noble gases, Alkaline earth metals). Over the years, new elements were discovered and put into the rough outline that Mendeleev created.
I hope that is about what you wanted.
Answer:a weak acid and a weak base
Explanation:
I think the correct answer would be HCl + NaHCO3 -> NaCl + H2O + CO2, 2HCl + CaCO3 -> CaCl2 + CO2 + H2O, 2HCl + Mg(OH)2 -> MgCl2 + 2H2O. Hydrochloic acid would react with the basic substances in the stomach which are magnesium hydroxide, sodium bicarbonate and <span>calcium carbonate.</span>
The correct answer is + 32.5 J because heat is absorbed here by copper not evolved also after calculation we will find the H value is positive, lets calculate it:
H = m C Δt where:
m = 10 g
C = 0.13 J/g.°C
Δ t = final temperature - initial temperature = 50 - 25 = + 25 °C
so H = 10 x 0.13 x (+25) = + 32.5 J
