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Questions in chemistry

📝 Answered - The half-life of a particular radioactive substance is 5 months. If you started with 100 grams of this substance, how much of it would remain after 10 months? Remaining Amount $= I (1-r)^{ t }$ [?] grams Round your answer to the nearest whole number.

📝 Answered - Activity No. 1: Observing the Shape of Solids, Liquids, and Gases Objective: (a) Describe the properties of solids, liquids, and gases in terms of shape. (b) Differentiate the distinct shapes exhibited by the three states of matter: solid, liquid, and gas through hands-on exploration and observation. Materials Needed: - Stone - Water - Three balloons Instructions: 1. Gather and work in groups. 2. Together with your classmates, perform the activity. Procedure: 1. Put the stone into one balloon and tie the top of the balloon. 2. Fill another balloon with water and tie it. 3. Blow up the third balloon with air and tie it. 4. Press the stone, water, and air in the three balloons and observe the changes in shape. Based on your observations, answer the following questions: - What happened to the shape of the stone when you pressed it? - What happened to the shape of the gas and liquid when you pressed them?

📝 Answered - The molar mass of calcium chloride ($CaCl_2$) is $110.98 g/mol$. If you were to calculate the number of moles in 23.4 g of $CaCl_2$, which example shows the correct way to set up the calculation? A. $23.4 g CaCl_2 \times \frac{110.98 g CaCl_2}{1 mole CaCl}$ B. $23.4 g CaCl_2 \times \frac{1 mole CaCl_2}{110.98 g CaCl_2}$

📝 Answered - Which of the following is a balanced equation representing the decomposition of lead(IV) oxide? A. [tex]2 PbO \longrightarrow 2 Pb+ O _2[/tex] B. [tex]PbO \longrightarrow Pb + O[/tex] C. [tex]PbO \rightarrow--> Pb + O _2[/tex] D. [tex]PbO _2 \rightarrow Pb+ O _2[/tex]

📝 Answered - How many grams of HCl are needed to make 200.0 mL of a 3.0 M solution? HCI: 36.46 g/mol

📝 Answered - Consider the reaction [tex]H _2(g)+ I _2(g) \Leftrightarrow 2 HI ( g )[/tex]. What is the reaction quotient, [tex]Q[/tex], for this system when [tex][ H _2]=0.100 M[/tex], [tex][ I _2]=0.200 M[/tex], and [tex][ HI ]=3.50 M[/tex]?

📝 Answered - 24.08 x 10^21 molecules of solute are present in 1000 ml of its solution. What is the concentration of the solution?

📝 Answered - In an experiment, a 0.3621 g sample of 1,8-octanediol (C₈H₁₈O₂) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.005 × 10³ g of water. During the combustion, the temperature increases from 23.22 to 25.58 °C. The heat capacity of water is 4.184 J·g⁻¹·°C⁻¹. The heat capacity of the calorimeter was determined in a previous experiment to be 930.9 J·°C⁻¹. Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of 1,8-octanediol based on these data. C₈H₁₈O₂(s) + (23/2)O₂(g) → 9H₂O(l) + 8CO₂(g) + Energy Molar Heat of Combustion = ______ kJ/mol

📝 Answered - (1) In guanidine NH=C(NH2)(NH2), nitrogen labelled as 1 is most basic. (2) Allyl carbocation is less stable than vinyl carbocation. (3) +I effect is exhibited by -NH3. (4) CH2Cl2 is non-polar solvent.

📝 Answered - If the activation energy required for a chemical reaction were reduced, what would happen to the rate of the reaction? A. The rate would increase. B. The rate would decrease. C. The rate would remain the same. D. The rate would be zero.