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11 Nov 2019
Cement is primarily composed of calcium silicate compounds whose formulas can be represented as (CaO)_x. SiO_2. When cement is mixed with water and sand, it forms concrete. An important factor in the physical characteristics of concrete is its cement content. During highway construction, an important quality control test is to routinely sample the concrete mix and determine its CaO content. A 76.12 g concrete sample was treated with a 150.00 mL aliquot of 2.099 M standard HCl. The HCl reacts with the CaO of the cement according to the equation: CaO + 2 HCl rightarrow CaCl_2 + H_2O After the reaction is complete, the sample was stirred thoroughly. From this sample, a 25.00 mL aliquot was removed and placed into an Erlenmeyer flask. Phenolphthalein is added and the excess HCl was titrated with 1.066 M NaOH. A volume of 41.01 mL of NaOH was required to reach the endpoint. Calculate the mass percent of CaO in the concrete sample in the following steps. (a) Calculate the concentration of excess HCI titrated by NaOH in the reaction mixture aliquot. M HCl (b) Calculate the number of moles of HCl that reacted with CaO. mol HCl(reacted w/CaO) (c) Calculate the mass of CaO in the sample. g CaO (d) Calculate the mass percent CaO in the concrete. % CaO
Cement is primarily composed of calcium silicate compounds whose formulas can be represented as (CaO)_x. SiO_2. When cement is mixed with water and sand, it forms concrete. An important factor in the physical characteristics of concrete is its cement content. During highway construction, an important quality control test is to routinely sample the concrete mix and determine its CaO content. A 76.12 g concrete sample was treated with a 150.00 mL aliquot of 2.099 M standard HCl. The HCl reacts with the CaO of the cement according to the equation: CaO + 2 HCl rightarrow CaCl_2 + H_2O After the reaction is complete, the sample was stirred thoroughly. From this sample, a 25.00 mL aliquot was removed and placed into an Erlenmeyer flask. Phenolphthalein is added and the excess HCl was titrated with 1.066 M NaOH. A volume of 41.01 mL of NaOH was required to reach the endpoint. Calculate the mass percent of CaO in the concrete sample in the following steps. (a) Calculate the concentration of excess HCI titrated by NaOH in the reaction mixture aliquot. M HCl (b) Calculate the number of moles of HCl that reacted with CaO. mol HCl(reacted w/CaO) (c) Calculate the mass of CaO in the sample. g CaO (d) Calculate the mass percent CaO in the concrete. % CaO
Bunny GreenfelderLv2
22 Feb 2019