Integrating Content, Inquiry anti Reasoning An unknown Group I metal carbonate M

Question

Integrating Content, Inquiry anti Reasoning An unknown Group I metal carbonate M_2CO_3 (M = Li, Na or K) was reacted with excess 2 M HCI and the mass of CO_2 released was determined by mass difference. The initial mass of solid M_2CO_3 was 2.002 g and the mass of CO_2 released was 1.206 g. Write the balanced chemical equation for the reaction of M_2CO_3 with HCI. What it the mole ratio of CO_2 to M_2CO_3? Calculate the molar mass of the unknown metal carbonate and identify the Group I metal. The rate of reaction of 0.030 g of magnesium ribben with 1 M hydrochloric acid was studied at four different temperatures by measuring the time required for the magnesium metal to disappear. The following data was recorded. Calculate the number of moles of magnesium that reacted and the average reaction rate for each temperature. Convert each temperature to kelvins and plot the average reaction time versus temperature in the graph below. Predict how long the reaction would lake at 75 degree C. Using kinetic molecular theory and collision theory, explain why the absolute temperature scale (kelvins) is more appropriate than Celsius for explaining the effect of temperature .on reaction rate. Does the effect of temperature on reaction rate support the collision theory of chemical reactions?

Explanation / Answer

(1)

(a) M2CO3 + 2 HCl --------------> 2 MCl + CO2 + H2O

(b) From the above balanced equation,

mole ratio of M2CO3 and CO2 is 1:1

(c) moles of CO2 = 1.206 / 44 = 0.0274 mol

So, moles of M2CO3 = 0.0274 mol

Number fo moles = mass / molar mass

0.0274 = 2.002 / molar mass

Molar mass = 2.002 / 0.0274

Molar mass = 73.1 g/mol

It is nearer to molar mass of Rb.

So, the unknown group 1 metal is Rubedium , Rb

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