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Questions in chemistry

[Done] Which of the following elements may occur in the greatest number of different oxidation states? A. C B. F C. O D. Ca E. Na

[Done] What is the difference between endothermic and exothermic reactions?

[Done] Find the number of moles of argon in 452 g of argon.

[Done] What is the molar mass of the following compound, rounded to the nearest gram? \[ \text{Na}_2\text{S}_2\text{O}_3 \]

[Done] Identify the type of reaction in \[ \text{KBrO}_3(s) \rightarrow \text{KBr}(s) + \text{O}_2(g) \]

[Done] Suggest two reasons why the UK government wants to encourage recycling of iron and steel.

[Done] Why does some friction occur with seemingly smooth surfaces?

[Done] A disturbance in matter that carries energy from one place to another is called a wave.

[Done] How much heat is given off when 8 g of hydrogen reacts in the reaction: \[ 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}; \Delta H = -115.60 \text{kcal} \] a. -57.8 kcal b. -115.6 kcal c. -173.4 kcal d. -231.2 kcal e. -462.4 kcal

[Done] Balance the equation: \(...NO_2 + ...O_2 + ...H_2O = ...HNO_3\)