1)What is the enthalpy change(Q) when 60.0 g of NaOH is dissolved in one litre of water, given that the temperature of the solution increased by 15.8 °C? 2)Determine the value of Δ for this reaction, taking the specific heat capacity of water to be 4.2/⋅JgC∘ and assume that initial temperature is 22 degrees and final temperature is 17.9 degree Celsius. Give your answer in units of kilojoules per mole and to 1 decimal place. Remember to include a sign in your answer.

3) In a calorimetry experiment, how many Joules of heat are given off when 0.5 g of food sample is heated from 20 to 30 degree Celsius.(specific heat of water(c) is 4.18 J/gC) Write the equation and show your calculation

4) A 100ml of water is heated using a burner. If the ΔT=20 degree C .Find the heat energy change in kJ/g. (c = 4.186 joule/gram °C) .

5) quantity of water is heated from 25.0 °C to 36.4°C by absorbing 325 J of heat energy. What is the mass of the water? show your calculation

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

thats how its supposed to be