# Chemistry- formulas cards

June 2009: q23: Writing ionic equations:

Sr2+(aq)  +  2Cl-(aq)   +  2Na(aq) + SO4(2-)(aq)   =    SrSO4(s)+  2Na(s) + 2Cl(g)

• Balance the equation using state symbols
• Any solids or gases stay as they were before showing ions.
• Cross out any elements that appear on either side of the equation.

Sr2+(aq)  +  SO4(2-) =  SrSO4(aq)

2nd example: Write ionic equation for the reaction between Magnesium Chloride and Sodium hydroxide

• MgCl2(aq)  +  2NaOH(aq)  =  2NaCl(aq)  +  Mg(OH)2(s)
• Mg2+(aq)  +  2Cl-(aq)  +  2Na+(aq)  +  2OH-(aq)  =  2Na+(aq)  +  2Cl-(aq)  +  Mg(OH)2(s)
• Mg2+(aq)  +  2OH-(aq)  = Mg(OH)2(s)
?
• Created by: aggy98
• Created on: 14-12-14 15:43

## Calculating Moles

One method of determining the proportion of calcium carbonate in a coral is to dissolve a known mass of the coral in excess acid and measure the volume of carbon dioxide formed. In such an experiment, 1.13 g of coral was dissolved in 25 cm3 of hydrochloric acid (an excess) in a conical flask. When the reaction was complete, 224 cm3 of carbon dioxide had been collected over water using a 250 cm3 measuring cylinder.

Calculate the number of moles of CO2 produced:

•  224cm3/1000= 0.224 dm3.
• 0.224/24=0.009333...moles

Calculate the mass of 1 mole of CaCO3:

• Write equation(given in previos answer):  CaCO3(s) + 2HCl(aq) =  CaCl2(aq) + H2O(l) + CO2 (g)
• The Molar mass is: 40.1(ca) + 12(c) + 48(O3)= 100.1g
1 of 1