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Chemistry - Balancing Equations
The main gas used in a stink bomb is hydrogen sulfide.

Chemistry - Balancing Equations

This Chemistry quiz is called 'Chemistry - Balancing Equations' and it has been written by teachers to help you if you are studying the subject at high school. Playing educational quizzes is a user-friendly way to learn if you are in the 9th or 10th grade - aged 14 to 16.

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An understanding of the fundamental ideas in Chemistry is vital for Science students in high school. This quiz focusses on chemical formulae and reactions, and on balancing chemical equations.

How many atoms of hydrogen, sulfur and oxygen are there in sulfuric acid, formula H2SO4?
1, 1, 1
2, 2, 4
1, 1, 3
A small number after the symbol for an atom in the formula tells you how many of that atom are present. Seeing the symbol just on its own means that you only have one of that sort of atom
What non-metals are found in sodium silicate?
Sodium and silicon
Silicon and oxygen
Sulfur and hydrogen
Silicon and carbon
The name of a chemical will often indicate what elements are present. Sodium is a metal so, for this question, can be ignored. The non-metal part is the 'silicate'. The 'silic' indicates the element silicon and the 'ate' is a code that indicates that it is combined with oxygen. This rule works with most chemicals that you will learn about at high school, so something like phosphate indicates you have phosphorous combined with oxygen. Other useful parts of this chemical code are 'ite', which also indicates oxygen is in there, and 'ide' which indicates that the non-metal is there on its own
What do their names tell you about sodium sulfide and sodium sulfate?
Sodium sulfide is soluble in water, sodium sulfate is not
Sodium sulfate is highly flammable, sodium sulfide is not
Sodium sulfide is a solid, sodium sulfate is a gas
Sodium sulfate has oxygen atoms joined to the sulfur atoms but sodium sulfide hasn't
Chemical names do not tell you any of the physical or chemical properties of a compound so you can immediately dismiss the first 3 options
The main gas used in a stink bomb is the highly toxic hydrogen sulfide. What elements does this compound contain?
Only hydrogen and sulfur
Only hydrogen and sulfide
Hydrogen, oxygen and sulfur
Water and sulfur
Easy if you were paying attention to the useful comment of question 2! You should have been able to dismiss answers 2 and 4 because there is no such element as sulfide and water is a compound, not an element
How many atoms of oxygen in this thermal decomposition - CaCO3 ⇌ CaO +CO2
1 on the left, 2 on the right
1 on the left, 3 on the right
3 on the left, 3 on the right
3 on the left, 2 on the right
So the equation is balanced
You might find it easier to have a pen and paper handy for this and the rest of the questions. A student is balancing an equation that involves Na2SO4. She needs to have 6 atoms of sodium, how would she write this in her answer?
None of the above
Writing a large number in front of a formula multiplies everything in the formula by that number. Na2 tells her that there were 2 sodium atoms there to begin with so multiplying the formula by 3 would give her the 6 she needed. That would also increase the number of sulfur and oxygen atoms
Bill needs to balance an equation that involves aluminum oxide, formula Al2O3. He requires a total of 12 oxygen atoms to balance his equation. What should he write?
OK, getting the gist of things now? You should have immediately dismissed answers 2 and 3 as they change the formula
Balance the equation Na + H2O → NaOH + H2.
2Na + 2H2O → 2NaOH + H2
Na + 2H2O → NaOH + H2
2Na + H2O → 2NaOH + H2
2Na + 2H2O → 2NaOH + 2H2
There are 2 Na atoms, 4 H atoms and 2 O atoms on each side of the equation. All the other answers have different numbers of the atoms on both sides of the equation
Balance the equation for the reaction CuO + Al → Cu + Al2O3
2CuO + Al → 2Cu + Al2O3
3CuO + 2Al → 3Cu + Al2O3
3CuO + 3Al → 3Cu + Al2O3
CuO3 + Al2 → Cu + Al2O3
We hope that you didn't choose the fourth one - remember, do not change formulae to balance equations. In the exam, any formulae you are given for balancing equations will be correct. If you alter them, they will then be wrong
In a blast furnace, there are several chemical reactions. The main one for smelting the iron from the iron ore is Fe2O3 + CO → Fe + CO2.
Which numbers should be put in front of each formula in order to balance the equation?
no number, 2, no number, 2
3, 3, 2, 3
2, 2, 3, no number
no number, 3,2,3
Remember, start off by counting individual atoms on each side then see what you need to get the same on both sides of the equation
Author:  Kev Woodward

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