A chemist observed a gas being evolved in a chemical reaction and collected some

Question

A chemist observed a gas being evolved in a chemical reaction and collected some of it for analysis. It contains 80% C and 20% H. It was also observe that 500 ml. of the gas at 0 degree C and 760 torr weighed 0.6095g What is the empirical formula of the gaseous compound? a. CH b. CH_2 c. CH_3 d. CH_4 e. C_2H_2 What is the molecular weight of the gas? a. 26 b. 30 c. 40 d. 50 e. 55 What is the molecular formula of the gas? a. C_2H_2 b. C_2H_4 c. C_2H_6 d. C_2H_8 e. C_3H_8 What is the degree of hybridization for N in NCl_3 molecule? a. dsp^2 b. sp^2 c. sp^3 d. dsp^3 e. sp What is .he molarity of a solution containing 1.37 g of NaCl (formula weight 58.4) in 25.0 ml- of solution? a. 0 .120 M b. 0.0 598 M c. 0.179 M d. 0.0 154 M e. 0.938 M Sulfur combines with oxygen gas to from 6.4 grams of sulfur dioxide SO_2 with no reactants left over determine the following. The percent by mass sulfur and oxygen in SO_2 are: a.27.3%S, 72.7%0 b.50%S, 50%0 c.35%S, 65%0 d.64%S, 36%0 e. 20%S, 80%0 In the reaction CaCO_3 rightarrow CaO + CO_2, 100 g of CaCO_3 is observed to decompose upon heating into 56 grams of CaO and 44 grams of CO_2 This is an illustration of: a. the Law of Conservation of Matter c. the Law of Conservation of Energy e. the law of proportional mixtures b. the Law of Gravity d. the Law of Multiple Proportions Five grams (5.0 g) of H_2 are mixed with 10 0 g of O_2 to produce water 2H2 + O_2 rightarrow 2H_2O). Answer the following questions: Which would be the limiting reactant? Which reactant is in excess? a. H_2O_2 b. H_2O_2 c. O_2H_2 d. H_2H_2O

Explanation / Answer

23. C = 80/12 = 6.67

H = 20/1 = 20

divide by smallest factor

C = 1

H = 3

Empirical formula of gas,

c. CH3

24. molar mass of gas = (0.6695)(0.08205)(273)/(760/760)(0.500) = 30 g/mol

b. 30

25. molecular formula

c. C2H6

26. degree of hybridization of N in NCl3

c. sp3

27. molarity of solution = 1.37/58.4 x 0.025

e. 0.938 M

28. Percent mass S and O and SO2,

b. 50%S, 50%O

29. In the given decomposition reaction, 100 g CaCO3 forms 56 g CaO and 44 g CO2, depicts,

a. Law of conservation of matter

30. moles H2 = 5/2 = 2.5 mol

moles O2 = 10/32 = 0.3125 mol

for complete consumption of H2 we would need = 2.5/2 = 1.25 mol O2

since moles of O2 is greater than needed, the limiting reactant is, and excess reactant would be,

a. H2, O2

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