Explanation:
when an iron bar rust is an example of a chemical change in which a new substance is formed and the change is not easily reversible.for iron to rust moisture and air must be present.while when a substance freezes,it can be easily reversed through melting and no new substance is formed.this change is termed a physical change.
Answer:
45 neutrons
Explanation:
Bromine has 35 protons and a mass number of 80. a) How many neutrons does the atom of bromine have? The mass number = protons + neutrons. Bromine has a mass number of 80 and 35 protons so 80-35 = 45 neutrons.
B, E, F have 3 significant figures
Answer:
A) litmus is red
Explanation:
To answer this question, it can be helpful to have the color charts. Litmus, phenolphthalein and methyl orange are ways to test the pH of a substance.
<u>Litmus paper</u>
Litmus can tell you if a substance is an acid or a base. You need to put the substance on both red litmus and blue litmus paper.
pH < 7: both papers are red. 3.0 is less than 7.
pH = 7: none of them change color
pH > 7: both papers are blue
<u>Phenolphthalein</u>
When this indicator is added to a substance, the result is either colorless or pink.
0 < pH ≤ 7: colorless. The color is not red or blue for pH 3.0.
pH > 7: pink
<u>Methyl orange</u>
0 < pH < 4: red. The color is not yellow if the pH is 3.0.
4 ≤ pH < 5: orange
pH ≥ 5: yellow
Answer:
Na2S, (NH4)3PO4
Explanation:
We can decide what compounds are soluble by considering the solubility rules that apply.
CdCO3 is not soluble in water because all carbonates are insoluble except those of ammonium, sodium and potassium.
Na2S is soluble in water because all sulphides are insoluble except those of sodium, potassium and ammonium.
PbSO4 is insoluble in water because all sulphates are soluble except those of lead and barium. The sulphate of calcium is only slightly soluble in water.
(NH4)3PO4 is soluble in water because all phosphates are insoluble except those of sodium, potassium and ammonium.
Hg2Cl2 is insoluble in water because all chlorides are soluble except those of lead, mercury II and silver.
