Mg + 2H(NO)3 ⇒ Mg(NO3)2 + H2
a specific hypothesis to test with a controlled experiment
When water freezes into ice, some of the properties have change. What stays the same.
Answer: 1: Ice Melting is a physical change. When liquid water (H2O) freezes into a solid state (ice), it appears changed; However, this change is only physical as the the composition of the constituent molecules is the same: 11.19% hydrogen and 88.81% oxygen by mass.
Have a goood day!
Answer:
Honey is an homogeneous mixture
Salsa is an heterogeneous mixture
Explanation:
Honey is a sweet uniformly colored liquid that can be of a dark variety or of clear golden color. Honey is made in nature by bees from flower nectar and is used as a food additive or sweetener
Honey is a homogeneous mixture because the concentration of the components of honey are uniformly distributed throughout the mixture. Every portion has the same concentration of components
Salsa is a sauce made by mixing chopped tomatoes, onions, chilies, lime juice and seasoning and therefore consists of both solid and liquid components mixed in varying proportion such that part will have continuous that comes in between different types of solid and no two parts have exactly the same composition
Therefore, salsa is an heterogenous liquid.
Answer:
- <u><em>It is positive when the bonds of the product store more energy than those of the reactants.</em></u>
Explanation:
The <em>standard enthalpy of formation</em>, <em>ΔHf</em>, is defined as the energy required to form 1 mole of a substance from its contituent elements under standard conditions of pressure and temperature.
Then, per defintion, when the elements are already at their standard states, there is not energy involved to form them from that very state; this is, the standard enthalpy of formation of the elements in their standard states is zero.
It is not zero for the compounds in its standard state, because energy should be released or absorbed to form the compounds from their consituent elements. Thus, the first choice is false.
When the bonds of the products store more energy than the those of the reactants, the difference is:
- ΔHf = ΔHf products - ΔHf reactants > 0, meaning that ΔHf is positive. Hence, the second statement is true.
Third is false because forming the compounds may require to use (absorb) or release (produce) energy, which means that ΔHf could be positive or negative.
Fourth statement is false, because the standard state of many elements is not liquid. For example, it is required to supply energy to iron to make it liquid. Thus, the enthalpy of formation of iron in liquid state is not zero.
