Answer:
here:
Explanation:
The changes in temperature caused by a reaction, combined with the values of the specific heat and the mass of the reacting system, makes it possible to determine the heat of reaction.
Heat energy can be measured by observing how the temperature of a known mass of water (or other substance) changes when heat is added or removed. This is basically how most heats of reaction are determined. The reaction is carried out in some insulated container, where the heat absorbed or evolved by the reaction causes the temperature of the contents to change. This temperature change is measured and the amount of heat that caused the change is calculated by multiplying the temperature change by the heat capacity of the system.
The apparatus used to measure the temperature change for a reacting system is called a calorimeter (that is, a calorie meter). The science of using such a device and the data obtained with it is called calorimetry. The design of a calorimeter is not standard and different calorimeters are used for the amount of precision required. One very simple design used in many general chemistry labs is the styrofoam "coffee cup" calorimeter, which usually consists of two nested styrofoam cups.
When a reaction occurs at constant pressure inside a Styrofoam coffee-cup calorimeter, the enthalpy change involves heat, and little heat is lost to the lab (or gained from it). If the reaction evolves heat, for example, very nearly all of it stays inside the calorimeter, the amount of heat absorbed or evolved by the reaction is calculated.
1) Dalton stated that atom is matter that can not be divided, but it is proved that the atom can be divided into subatomic particles (electrons, protons and neutrons).
2) He stated that atoms of one element can not be changed into atoms of other elements, but now that is possible by nuclear reactions.
Today we still use his postulate: Atoms combine in the ratio of small whole numbers to form stable compounds, for example H₂O.
Answer:
Explanation:
Molarity is a measure of concentration in moles per liter.
The molarity of the solution is 1.2 M NaNO₃ or 1.2 moles NaNO₃ per liter. There are 0.25 liters of the solution. The moles of solute are unknown, so we can use x.
- molarity= 1.2 mol NaNO₃/L
- liters of solution=0.25 L
- moles of solute =x
We are solving for x, so we must isolate the variable, x. It is being divided by 0.25 liters. The inverse of division is multiplication, so we multiply both sides by 0.25 L.
The units of liters cancel, so we are left with the units moles of sodium nitrate.
There are 0.3 moles of sodium nitrate.
Density can be calculated using the following rule:
density = mass / volume
therefore,
mass = density x volume
From the givens:
we have the density = 1030 kg/m^3 and volume = 1.89 m^3
Substitute in the equation to get the mass as follows:
mass = 1030 x 1.89 = 1.9467 x 10^3 kg
For alpha and beta decay it does because the proton number changes.
During gamma, there is no change of identity, just energy
